Showing papers in "Biological Journal of The Linnean Society in 1995"

Evolution and present situation of the South American Camelidae

Abstract: This paper provides a review of South American camelid evolution, classification and present status. Particular attention is paid to the debate concerning origins of the domestic alpaca and llama and the contribution of research on faunal remains from Andean archaeological sites towards resolving this issue. Changes in incisor morphology during the domestication process suggest that the alpaca may be descended from the vicuna, while a comparison of fibre production characteristics in preconquest and extant llama and alpaca breeds indicates that extensive hybridization between the two species is likely to have occurred since European contact. The potential role of hybridization in the formation of extant South American camelid populations has not been studied, and may be the root cause of taxonomic disputes.

Why are there so many mimicry rings? Correlations between habitat, behaviour and mimicry in Heliconius butterflies

Abstract: In the new world tropics there is an extravagant array of sympatric butterfly mimicry rings. This is puzzling under strictly coevolutionary (Mullerian) mimicry: all unpalatable species should converge as ‘co-mimics’ to the same pattern. If mimicry has usually evolved in unpalatable species by one-sided (Batesian) evolution, however, it is easy to see that mimicry rings centred on different models could remain distinct. If mimicry rings were also segregated by habitat, a diversity of mimicry rings could be stabilized. In this paper we report correlations between behaviour and mimicry of nine unpalatable Heliconius species. It is already known that co-mimics fly in similar habitats, and non-mimics fly in different habitats, although there is much overlap. Contrary to a previous report, we find little difference in flight heights of heliconiine mimicry rings; all species fly from ground level to the canopy. However, co-mimics roost at night in similar habitats and at similar heights above the ground, but in different habitats and at different heights from species in other mimicry rings. Heliconius (especially the erato taxonomic group) are renowned for roosting gregariously; and co-mimics roost gregariously with each other more often than with non-mimics. Gregarious roosting is therefore common between species, as well as within species. There are thus strong links between mimicry and behavioural ecology in Heliconius. The paradoxical correlation between nocturnal roosting and visual mimicry is presumably explained by bird predation at dusk when roosts are forming, or at dawn before they have disbanded. Direct evidence of predation is lacking, but there are high rates of disturbance by birds at these times. These results, together with knowledge of the phylogeny of Heliconius, suggest that species from the melpomene -group of Heliconius have radiated to occupy mimetic niches protected by model species in the Ithomiinae and the erato -group of Heliconius. A variety of sympatric mimicry rings is apparently maintained because key models fail to converge, while more rapidly-evolving unpalatable mimics evolve towards the colour patterns of the models. The maintenance of mimetic diversity would be aided by the habitat and behavioural differences between mimicry rings revealed here, provided that different predators are found in different habitats. This explanation for the maintenance of multiple mimicry rings is more plausible for Heliconius mimicry than alternatives based on visual mating constraints, thermal ecology, or camouflage.

Ornaments or offspring: costs to reproductive success restrict sexual selection processes

Abstract: If, in their partner choice, males seek direct benefits (fecund females), the result will be selection for traits indicating female quality rather than for arbitrary (Fisherian) traits. However, the costs of developing and maintaining the sexually selected traits (ornaments) may reduce the resources available to the female for allocation to reproduction and hence result in lower reproductive success per brood. This hitherto unrecognized fecundity cost of sexually selected traits will constrain both the potency of sexual selection mechanisms and the degree of elaboration of sexually selected traits in females, and can also apply to males which invest in their offspring: sexual selection becomes self-limiting. The fitness implications of these costs are examined for both sexes in a variety of mating and parental care patterns. Sexual selection acting on both sexes may lead to either dimorphism or monomorphism, the latter being the case when the quality indicators chosen by both sexes coincide. Ways of evasion or reduction of these reproductive costs of allocations to sexually selected traits include using different resource components for the ornament and for reproduction, or partitioning the two allocations in time.

Patterns of body size changes in fossil and living equini (perissodactyla)

Abstract: The importance of body mass prediction from several cranial, dental and appendicular variables in living Equini are studied. Relationships between the body mass changes and the ecogeographic picture of Equini evolution are also analysed. The metapodial and phalanx variables, particularly antero-posterior diameters, are better correlated with body mass than cranial variables in living Equini. Large sized species are correlated with cold climates, open habitats and/or soft soils; small ones are correlated with warm climates, more closed habitats and/or hard soils. Pleistocene horses from Europe and Africa follow an evolutionary trend opposite to their North American counterparts, from larger sized species to smaller ones. In South America the pattern of body size is different to those of the other continents. Species of Hippidion reaching large body mass, whereas some species of Equus, E. andium, follow a diminishing trend.

Nectarivorous feeding mechanisms in bats

Abstract: Cranio-dental characteristics are quantified between micro- and megachiropteran nectarivores and compared with microchiropteran animalivores, frugivores, and megachiropteran frugivores. Microchiropteran nectarivores share many characteristics with megachiropteran nectarivores and frugivores, but differ in having a long, narrow head. Megachiropterans have wide zygomata, which would allow for more jaw musculature. Diminutive cheekteeth are characteristic of nectarivory in both suborders, but both have relatively large canines. Teeth in nectarivores can occupy as little as a tenth of the palatal area compared to nearly two-thirds in microchiropteran animalivores. The proportion that the dilambdodont stylar shelf occupies of molars in microchiropteran nectarivores can be as much as that in microchiropteran animalivores (insectivorous and carnivorous bats) or as little as that in microchiropteran frugivores but not as extreme as either. In addition to dimunitive teeth, nectarivores have fused mandibles and upper canines that are worn from contact with the lower canines (thegosis). These characteristics may be necessary for the lower jaw to support an elongated, mobile tongue. While microchiropteran nectarivory, frugivory, and carnivory probably evolved independently from an insectivorous microchiropteran ancestor, megachiropteran nectarivory probably evolved from megachiropteran frugivory or the reverse.

The potential role of large herbivores in nature conservation and extensive land use in Europe

Abstract: The concept of ecosystem restoration is gaining momentum in western Europe. This is necessary because in most managed nature reserves one or more of the following processes, which are analogous to those that have led to the dramatic loss of biological diversity in Europe, are still operating: continuing nutrient output, continuing high level of disturbance and fixing the system in some successional stage. This is partly because most management activities have been derived from, or copy, former agricultural practices. The study of natural ecosystems has revealed the key role large herbivores have in maintaining structural diversity in the vegetation and so biological diversity. Because of this they have been used as tools in achieving a variety of conservation goals. Here, various effects large herbivores can have on plant species composition, structural diversity of the vegetation and fauna are briefly reviewed. Attention is given to pasture-woodlands in southern Europe, which often have a relatively high biological diversity and share some key features with natural ecosystems: very low nutrient input, extensive grazing with large herbivores and the presence of natural tree cover. In a number of European countries attempts are being made to restore normal functioning multi-(herbivore) species ecosystems.

The adaptive significance of colour pattern polymorphism in the Australian scincid lizard Lampropholis delicata

Abstract: Females of Lampropholis delicata are dimorphic for colour pattern, the difference betweenmorphs being the presence or absence of a distinct white mid-lateral stripe. A less distinct striped morph occurs also in males. We evaluated alternative hypotheses for the maintenance of this polymorphism by examining temporal and spatial variation in morph frequency, testing for differential selection among morphs using data on body size and reproductive traits from preserved specimens, and experimentally manipulating colour pattern in free-ranging lizards of both sexes, to assess the influence of the lateral stripe on survival rates. We found that the relative frequency of striped individuals varied among populations and decreased from north to south in both sexes, coincident with an increasing incidence of regenerated tails. Morph frequencies did not change through time within a population. Striped gravid females appeared to survive better and produced larger clutches than did non-striped females. In our experimental study, the relationship between survival and colour morph differed between the two sexes; males painted with a white lateral stripe had lower survival than control (brown stripe) males, but survival did not differ between striped and control females. The different response in the two sexes may be due partly to differences in temperature and microhabitat selection. We propose that the white lateral stripe decreases susceptibility to predators in gravid females but increases risk of predation in males, especially in combination with low temperatures. The polymorphism might be maintained by: (l) opposing fitness consequences of the stripe in males and females; (2) sex-specific habitat selection; and (3) gene (low in combination with spatial variation in relative fitness of the two morphs.

Henderson Island prehistory: colonization and extinction on a remote Polynesian island

Abstract: Situated at the extreme margin of the Indo-West Pacific biotic province, the four islands of the isolated Pitcairn Group hold interest for biogeographers and archaeologists alike. Human settlement may have been as early as the 8th century AD for the uplifted limestone island of Henderson, the most pristine island of its kind. An archaeological survey of the Pitcairn Islands is provided, while Henderson is examined in detail. Recent extensive excavations provide a record of change during 600 years of human occupation. Adaptation to the ecologically-marginal conditions is documented by artefacts, more than 150 000 vertebrate bones, molluscs and subfossil plant remains recovered from stratigraphic contexts. The effects of prehistoric human occupation on the pristine environment are revealed by Polynesian plant and animal introductions, bird extinctions and range reductions, possible over-predation of marine molluscs, exploitation of sea turtles, and large-scale burning for swidden agriculture. The origin of human colonists is documented by analysing imported artefacts by geochemical characterization (x-ray fluorescence analysis). The human abandonment of Henderson, by the seventeenth century, is viewed in the context of prehistoric regional dynamics.

Evolution of nocturnality in bats: Potential competitors and predators during their early history

Abstract: Despite their taxonomic and ecological diversity, modern bats (Order Chiroptera) are almost exclusively nocturnal. This behaviour is too ubiquitous to be explained by common patterns of temporal variation in availability of their diverse food sources or by the risk of hyperthermia when flying during the day. Other explanations for bat nocturnality include competition and increased predation risk from birds during the day. In the early and mid Eocene, the known bat fauna consisted of several insectivorous species of sizes similar to those of the modern European assemblage. This fauna was contemporaneous with several species of predatory birds, including owls (Strigiformes), hawks (Accipitridae), falcons (Falconidae) and rollers (Coraciiformes), which were the same size as modern predators on bats. Predation risk could therefore have been a significant factor preventing the early bats from becoming diurnal. Competition from aerial insectivorous birds, however, was less likely to have been significant for bats during the early Eocene, since very few such groups, mainly small Aegialornithidae, were present, with most of the major groups of aerial insectivores evolving later.

Resistance to thermal stress in preadult Drosophila buzzatii: variation among populations and changes in relative resistance across life stages

Abstract: Resistance to a short term exposure to a high temperature stress was examined in eggs, larvae and pupae of Drosophila buzzfltii from seven localities. Across development, pupae were most resistant, followed by eggs, and then first and third-instar larvae. Variation among populations for resistance to heat stress was significant in all life stages. However, there was much less variation among populations where measured as eggs and pupae than for both first and third instar larvae. Older larvae showed large changes both in viability and developmental time, while exposure of young larvae to heat stress led to a decline in viability without delayed development. Populations that had the shortest developmental time at 25oC were relatively the most resistant to heat stress as larvae. High relative resistance at one preadult life stage was not necessarily associated with relatively high resistance at another, or with previous measurements of resistance for adults from these populations. Comparison of populations that were more similar in their pattern of change in resistance across development suggested a relationship with the climate of origin. The possibility that developmental variation in the expression of heat shock proteins may cause variation in resistance to thermal stress for different life stages is discussed.

Selection for pollination success and the mechanical fit of Impatiens flowers around bumblebee bodies

Abstract: Selection on flowers has often been viewed as being particularly strict, constant, and responsible for species differences. 1mpaliens pallida and I. capensis flowers fit snugly around bees, leading one to expect a close relationship between floral morphology and pollination success. My studies on the amount of pollen removed from androecia and deposited on stigmas in single visits by bumblebees did not confirm this supposition. Trimming off parts of the floral vestibule with scissors and gluing in pleats had very little effect on the amount of pollen that bees moved. In reciprocal transfer experiments, flowers from different populations sometimes differed in the amount of pollen moved, but when the two species were compared in sympatry, pollen removal and deposition differed hardly at all. A comparison of the relationship between pollen movement and floral morphology among 15 populations showed that, although there was great heterogeneity in the amount of pollen moved, the observed differences were independent of floral morphology. None of this supports a belief in strong selection that fine-tunes the mechanical fit between bee and flower; selection for visitation success based on pollinator behaviour may have a much stronger influence on floral characters.

From castaways to throwaways: marine litter in the Pitcairn Islands

Abstract: Pollution of the oceans by garbage is a serious problem. Worldwide, as many as 8 million items of garbage may enter the seas on a daily basis. These items may survive some time, drifting in the oceans and give rise to other environmental problems such as causing hazards to wildlife (through ingestion and entanglement) before being washed ashore. Surveys of beaches on Ducie and Oeno Atolls in the Pitcairn Islands were compared with a similar survey on a beach in S.W. Ireland. The three beaches were similar in the density and major categories of garbage to be found, but differed in subtle ways. For example the Pacific beaches had a greater proportion of bottles and buoys, whereas the Irish beach had a greater proportion of sweet wrappers and polythene bags. Although these remote islands may be thousands of miles from industrial centres their beaches are apparently as dirty as those in Europe.

Karyotype and genetic evolution in speciation of subterranean mole rats of the genus Spalax in Turkey

Abstract: Karyotype (2n) and allozyme diversity at 37 gene loci were determined in 69 subterranean mole rats in Turkey belonging to the two superspecies: the ancestor Spalax leucodon (n = 55; 20 populations) and the descendant S. ehrenbergi (n = 14: four populations. We identified remarkable variation of diploid chromosome numbers in the S. leucodon superspecies: 2n = 38, 40, 50, 54, 60 and 62; and in the S. ehrenbergi superspecies: 2n = 52, 56 and 58. Genetic diversity indices were low on average in both S. leucodon and S. ehrenbergi superspecies: Allele diversity, A = 1.081 and 1.074; polymorphism, P-50 0 = 0.077 and 0.068; heterozygosity, H = 0.038 and 0.027; and gene diversity, H = 0.038 and 0.034, respectively. H ranged from 0 in mesic or semimesic regions to 0.088 in arid Anatolia. We consider the populations with different diploid chromosome numbers, 2n, as good biological species. Karyotypic diversity may mark extensive ecological speciation. Nee's genetic distances, D average 0.174, range 0.002 0.422) and ecogeographical criteria suggest that almost each population may represent a different biological species, but critical future testing is necessary to support this claim. Karyotypes and allozymes are nonrandomly distributed across Turkey, displaying remarkable correlations with climatic and biotic factors. Both 2n and H are significantly correlated with aridity stress (2n/rainfall. r = −0.74; P < 0.001), and in our region also with climatic unpredictability. These results support the niche-width genetic variation hypothesis in space and time. Climatic selection in Turkey appears to be a major architect of karyotype and genetic (allozyme) diversity and divergence in mole rat evolution, in both speciation and adaptation.

Facultative polygyny and habitat succession in boreal ants

Abstract: High dispersal risks of ant queens make staying in the natal patch more attractive than long range dispersal. These alternative strategies and the mode of colony founding determine the average number of queens in the population. Increasing competition and queen predation make independent colony founding increasingly difficult and the only option for new queens to reproduce in the habitat patch may be to enter an existing colony. The effect of nest-site availability to the number of queens was studied in successional spruce-dominated taiga forests in facultatively polygynous ants Myrmica ruginodis, M. sulcinodis, Leptothorax acervorum, Formica sanguinea and F. truncorum. Decreasing relatedness among worker nestmates supports an association between increasing habitat age and polygyny to some extent. M. sulcinodis and L. acervorum persist in this type of taiga only for a relatively short period. Relatedness varied only slightly among populations, but lower relatedness estimated in other studies suggested higher levels of polygyny in older populations. In M. ruginodis there was more variation in relatedness and it was possibly connected to the relative proportions of the two social forms of the species. In F. sanguinea and F. truncorum the decrease in relatedness with increasing age of the habitat was clearest. Other factors favouring limited dispersal and acceptance of new queens in the colonies are, however, hard to separate.

The conservation of declining butterfly populations in Britain and Europe: priorities, problems and successes

Abstract: The status, ecology and conservation of butterflies in Europe and Britain are reviewed, as a background to the National Trust's past and future contribution to British conservation. Britain has a poor butterfly fauna by European standards, the main areas of endemism and species richness being in the Alps and southern Europe. To date, the main declines among European butterfly populations have occurred across central-northern Europe, with slightly higher extinction rates in mainland countries than in Britain. The main causes of decline are biotope destruction, the loss of certain species' habitats within surviving semi-natural biotopes due to changed land management, and a failure by several species to track the patches of their habitat that are still being generated in modern fragmented landscapes. Until recently, most conservation programmes failed to take account of the latter two factors, resulting in many local extinctions of rare butterfly species even in conservation areas. Recent measures have been much more successful; many were first tested on National Trust properties.

Life-cycle regulation and life history plasticity in the speckled wood butterfly: are reaction norms predictable?

Abstract: We investigated whether interpopulational variation in life-cycle regulation and life-history plasticity, in response to photoperiod, is predictable from considerations of what would be the adaptive life cycle and life history in a given environment. The investigation was performed on five populations of the speckled wood butterfly,Pararge aegeria(L.) (Lepidoptera: Nymphalidae), from central and south Sweden, England, Spain and Madeira. Insects from all five populations were reared at all daylengths from 10 h to 20 h at 17∘C. Larval and pupal development times were noted. Predictions were met regarding the type of life-cycle regulation and the shape of reaction norms. Evidence for diapause (larval summer and winter diapause, pupal winter diapause) was found in the three northern populations (P. a. tircis) but not in the two southern populations (P. a. aegeria). Photoperiodic thresholds for diapause induction followed the predicted latitudinal patterns, and this was also the case regarding quantitative regulation of development time (by photoperiod) among directly developing individuals. Under direct development, development time was progressively shorter in shorter daylengths in the two Swedish populations, where this signals progressively later dates. This was not found in the English, Spanish and Madeiran populations where such a response is likely to be maladaptive, because one or more generations of larvae are present before summer solstice. There were also unexpected results, for which we propose preliminary adaptive explanations.

Ecological restoration and creation: a review

Abstract: A European-wide review of habitat restoration and creation is presented which identifies the substantial loss of habitats and the increasing fragmentation and isolation of those that remain as the key raison d'etre for initiatives to rehabilitate and re-establish habitats. Progress in this is exemplified by reference to the reinstatement of traditional management, the problems associated with reducing loadings, and the control of invasive alien species. Habitat repair after damaging activities is illustrated through discussion of advances in dwarf-shrub heath and grassland re-establishment. It is concluded that a wealth of knowledge is now available on which to base appropriate action, and that, provided the desired species persist, restoration is, to some extent, achievable. Some of the principles involved in habitat creation are outlined. Provided these are observed, such establishment can play a vital role in nature conservation, although there is scope for more innovative schemes and basic research into some of the issues involved.

Evolutionary influences on body size in free-living and parasitic isopods

Abstract: The influence of mode of life and habitat characteristics on the evolution of body size in isopods was investigated in a comparative analysis based on data from 746 free-living and parasitic species. The phylogeny of isopods allowed 24 independent comparisons to be made between higher taxa (families or superfamilies), each corresponding to a separate branching event. The evolution of parasitism was consistently associated with reductions in body size. On the contrary, invasion of freshwater habitats was consistently coupled with increases in body size. Lineages moving to higher latitudes were significantly more likely to evolve larger body sizes than those shifting toward the equator. In addition, colonizing deeper water resulted in a weak tendency to evolve larger body size. The analysis suggests that the large size of some isopod groups parasitic on fish (e.g. Cymothoidac) may have been inherited from a free-living ancestor and is not the product of directional selection toward large size and greater fecundity.

Differential predation on sexes affects colour polymorphism of the isopod Idotea baltica (Pallas)

Abstract: Variable selection, including spatio-temporal variation, frequency-dependent selection and differential selection due to habitat choice, may maintain polymorphism in heterogeneous environments. We studied predation as a selective agent on colour polymorphism of the aquatic isopod I. baltica Variable predation on this species can arise from at least three sources. First, apostatic selection was studied by testing the formation of preferences on colour morphs in the perch, a common predator of I. baltica . Such acquired preferences should induce apostatic selection. While our results indicate some acquired preferences, there was significant heterogeneity in the behaviour of predator individuals. Second, temporal variation in selection can arise due to habitat shift from the green algae juvenile habitat to the bladderwrack adult habitat, and the consequent change in the crypsis of the morphs. Different crypsis between sexes probably promoted high predation mortality among females in the juvenile habitat. The high rate of male mortality during the breeding period, on the other hand, was presumably due to their high mate-searching activity. Third, the sexdependent habitat choice of I. baltica leads to sexual differences in the susceptibility of morphs to predation. Predators preferred the white-spotted morph over the uniform one in males but not in females, supporting the `dimorphic niche' hypothesis as an explanation of sexual differences in morph frequencies. Finally, no evidence was found that the colouration patterns were under sexual selection. We therefore conclude that variable predation is the most promising explanation for the maintenance of polymorphism in I. baltica

The flora of the Pitcairn Islands: a review

Abstract: The vascular plant flora of the Pitcairn Islands, south-central Pacific Ocean, is described based on extensive new collections made in 1991 and previously published records. Two vascular plants occur on Ducie Atoll; one ( Pemphis acidula ) is a new record. Sixty-three native vascular plants occur on Henderson, of which nine are endemic; Canavalia rosea , Operculina turpethum , Psilotum nudum and Solanum americanum are new records for the island. Oeno Atoll has 16 native vascular plants; the single endemic ( Bidens hendersonensis var. oenoensis ) was not found in 1991 despite careful searches. Triumfetta procumbens was new for Oeno. Sixty-six native vascular plants have now been recorded from Pitcairn Island, there are two endemic ferns and seven endemic angiosperms in this number. A number of non-native taxa were new to Pitcairn. Some of the previously described taxa could not be found on Pitcairn, probably because they are very rare and only a small amount of time was spent collecting on Pitcairn. Many of the Pitcairn taxa are threatened by the spread of introduced species, especially Syzygium jambos

Pasture‐woodland and its conservation in Britain

Abstract: Pasture-woodland occurs as a wide range of types in Britain. It is particularly important for nature conservation in terms of its lichen, invertebrate and bird populations, and also for bat roosts and probably fungi. Its interest tends to complement that of coppice woods, the other major form in which ancient semi-natural woodland has survived. Pasture-woodland (including pollard trees) is widespread in Europe, but British examples of international importance have been identified. It is under threat from over-grazing and consequent lack of regeneration, but also some of its characteristic species may be lost if grazing is removed altogether. The lichen component of pasture-woodland is particularly sensitive to air pollution, while removal of fallen dead wood and felling of old trees may damage the invertebrate interest. There is a major need to produce site inventories and descriptions, to raise awareness of the special value of pasture-woodland, and to implement more widely me site management techniques that are being used successfully on a number of key sites at present. The isolation of many sites cannot be reduced in the short term, but in general terms old trees in the countryside must not be allowed to diminish further.

Patterns in species description: a case study using the Geometridae (Lepidoptera)

Abstract: The described fauna is not a random sample of extant species. However, patterns in species description remain poorly documented. In this paper we explore the dynamics of description of geometrid moths, one of the most speciose families of Lepidoptera. The numbers of species described per decade peaked around 1890 to 1910, and the cumulative number of described species has yet to reach an asymptote. Growth in the cumulative numbers of described species has taken a variety of forms in the different biogeographic regions. The distributions of the numbers of authors describing different numbers of species, and of the numbers of synonyms per valid species name, are both strongly right-skewed. The number of synonyms associated with a valid species name is negatively correlated with the year in which that name was published, and the numbers of synonyms and valid species names are positively correlated both across subfamilies and biogeographic regions. Such patterns provide an important foundation from which to explore underlying spatial patterns in the species richness of speciose higher taxa.

The breeding biology of the gadfly petrels Pterodroma spp. of the Pitcairn Islands: characteristics, population sizes and controls

Abstract: This paper reports the breeding biology and nesting seasons of the gadfly petrels which nest on the four islands of the Pitcairn group, Pitcairn, Henderson, Oeno and Ducie. The species currently breeding are Murphy's petrel Pterodroma ultima , Kermadec petrel P. neglecta , Herald petrel P. heraldica and Henderson petrel P. atrata . Of these, Murphy's petrel is the most numerous; an estimated 250 000 pairs bred on Ducie, which is probably the major breeding station of the species. Novel basic breeding data for Murphy's petrel are presented. Incubation spells, averaging 19.3 days, are exceptionally long for a petrel. Phoenix petrel P. alba appears to have ceased to breed on the Pitcairn Islands since the 1922 surveys of the Whitney Expedition. Nesting success was low on Henderson Island during the study. For all four breeding species, less than 20% of eggs laid yielded fledglings. Failure occurred at the early chick stage and observations indicated that it was due to predation by Pacific rats Rattus exulans. Although rats are present on Ducie, predation was apparently less severe there. The situation on Oeno may be intermediate. I consider how the populations of Henderson are maintained in the face of this intense predation. The Murphy's petrel population may be sustained by immigration from Ducie while the Herald and Henderson petrel populations could be undergoing a long-term decline on Henderson. It is not clear how the Kermadec petrel population is maintained. The conservation implications of these findings are discussed.

One hundred million years of competitive interactions between bryozoan clades: asymmetrical but not escalating

Abstract: Direct evidence of competition is seldom available from the fossil record. Overgrowth relationships of encrusting marine organisms constitute an exception but have previously been reported in only temporally and geographically local occurrences. Results of overgrowths between members of two bryozoan clades, the Cyclostomata and the Cheilostomata, have been compiled for faunas distributed through the past 100 Myr. The cheilostomes have consistently out-competed the cyclostomes, with approximately 66% overgrowth success through the entire interval. This difference in success in direct interactions along with the Mid-Cretaceous rapid radiation of cheilostomes is interpreted as a factor in the Mid- to Late Cretaceous reversal from the previous diversification to stasis or gradual decline of cyclostome diversity.

Phylogenetic analysis of G-banded karyotypes among the South American subterranean rodents of the genus Ctenomys (Caviomorpha: Octodontidae), with special reference to chromosomal evolution and speciation

Abstract: The chromosomes of subterranean rodents of the South American genus Clenomys are highly variable with diploid numbers ranging from 10 to 70 The Phylogenetic relationships of this group have been analysed cladistically using G-banded karyorypes as have the chromosomal rearrangements involved in its karyotypic differentiation One group, called the 'Corrientes group', has very variable chromosomes but low allozymic and morphological differentiation among its members This group has been analysed with respect to chromosomal speciation Using a member of another subfamily ( Octodonlomys gliroides ) as an outgroup, the results indicate that karyotypes with low diploid and fundamental numbers are plesiomorphic The range of diploid numbers studied here is between 22 and 70, while the fundamental numbers are between 40 and 86 It was found that the main chromosomal rearrangement that transforms karyotypes towards higher diploid and fundamental numbers is the acquisition of new chromosomal material via unknown mechanisms, followed by pericentric inversions that generate new chromosomal arms, centric fusions and centric fissions In spite of their low differentiation regarding allozymic and morphological features, it was found that the karyomorphs of the Corrientes group have enough chromosomal differentiation to consider them as distinct species Beside the range of diploid and fundamental numbers of this group (42–70 and 80–84 respectively), their pairwise chromosomal differences are high The most closely related of them differ in one nonhomologous arm, one Robertsonian change and a whole chromosome duplication The most differentiated taxa differ in 20 arms with lack of homology, 12 Robertsonian changes (one with monobrachial homology), six pericentric inversions and the above mentioned probable arm duplication For these reasons, it is probable that some kind of chromosomal speciation has occurred in the Corrientes group

Genetic differentiation of aquatic snails (Gastropoda: Hydrobiidae) from artesian springs in arid Australia

Abstract: Electrophoretic surveys of 10 species of hydrobiid snails in two indigenous genera ( Fonscochlea and Trochidrobia ) living in arid-zone artesian ‘mound’ springs are reported. The study is based on 96 populations of hydrobiid snails living in 32 different springs representing 18 spring groups in the Lake Eyre Supergroup, northern South Australia. The species-level taxonomy of these snails, previously based on morphological differences alone, was tested and modified. The snails were examined within five clear-cut morphological groups: the two largest, fully aquatic species ( Fonscochlea accepta and F. aquatica ) were treated independently, as was the amphibious F. zeidleri The morphologically similar three smaller aquatic species were investigated as a group. Within this group one new species is described and, on the basis of the genetic evidence, two others ( F. variabilis and F. conica ) are considered conspecific. The four species of Trochidrobia are investigated together and T. punicea separately in more detail. Sympatry between Trochidrobia smithi and T. punicea is recorded for the first time. The springs are arranged in an essentially linear pattern and genetic differentiation largely follows an isolation by distance model, although there is a significant genetic discontinuity between two nearby spring groups, Beresford/Warburton Springs and Strangways Spring, which is presumably the result of differential historical continuity of spring habitat. The size of the spring influences the degree of genetic difference between springs within spring groups, with small springs attaining greater levels of differentiation than large springs. The findings suggest that if genetic diversity is to be conserved, current management strategies protecting only single springs within a group are inadequate. Despite the considerable number of indigenous species found in these springs, currently all remain on pastoral leases and some are threatened by the continuing expansion of water extraction from the Great Artesian Basin.

Limitations to the inference of gene flow at regional geographic scales--an example from the Pieris napi group (Lepidoptera: Pieridae) in Europe

Abstract: We used hierarchical and pairwise F-statistics to describe genetic differentiation and infer gene flow (M) on local and regional scales within and among parapatric European butterfly taxa in the Pieris napi (L.) group. Within-population allozyme variability is consistently high, and local effective population sizes are inferred to be in the thousands of individuals. The pairwise analysis yields an average neighbourhood area of radius 3.5 km. Among populations within most regions, differentiation is low and M > 2 effective individuals population−1 generation−1. Pairwise comparisons within the britannica group show a disjunction indicating that it is out of equilibrium, perhaps as a result of secondary contact between highland and lowland groups. Comparison between meridionalis groups on mainland Italy and Corsica yields M > 12 ; this is surely too high and lack of equilibrium resulting from initial colonization is suspected. The hierarchical analysis indicates that 23 ⩽ M ⩽ 88 among the taxa napi, bryoniae and meridionalis that meet in hybrid zones; no effective gene flow barrier exists among them. This high estimate could also result from recent primary contact, but such a genetic barrier should produce the ‘edge effects’ seen in population genetic simulations, and no evidence of this was found among geographically close samples of napi and bryoniae populations from Switzerland. Studies of gene flow among geographic regions are greatly limited by the equilibrium assumption, though studies of local differentiation are much less so. Population studies of gene flow on local scales at regional boundaries provide limited means of testing the equilibrium assumption, and both regional and local analyses provide testable predictions about local population structure. When the equilibrium assumption is not upheld, local patterns at regional boundaries can provide historical information about primary vs. secondary contact.

Resolution of portions of the kangaroo phylogeny (Marsupialia: Macropodidae) using DNA hybridization

Abstract: We generated a DNA hybridization matrix comparing eleven ‘true’ kangaroos (Macropodinae) and two outgroup marsupials, the rufous rat-kangaroo Aepyprymnas rufescens (Potoroinae) and the brush-tailed phalanger Trichosurus vulpecula (Phalangeridae). A small matrix included additional species of the genus Macropus (large kangaroos and wallabies). The results indicate that the New Guinean forest wallaby Dorcopsulus vanheurni , and the quokka Setonix brachyurus, represent successively closer sister-groups of other macropodines. The remaining taxa examined form two clades: the tree kangaroo Dendrolagus matschiei with the pademelons Thylogale and rock wallabies Petrogale , and Macropus including the swamp wallaby Wallabia bicolor . The smaller matrix of five Macropus species and Wallabia (with Dorcopsulus as an outgroup) pairs the red-necked wallaby M. rufogriseus and Parry's wallaby M. parryi , with the eastern grey kangaroo M. giganteus as their nearest relative; and associates the red kangaroo M. rufus and wallaroo M. robustus , with Wallabia as their sister-taxon. In the larger study, we found that inclusion of both outgroups provided little resolution among the macropodines, judging by jackknife and bootstrap tests. When Aepyprymnus was deleted, the Dendrolagus-Thylogale-Petrogale association obtained; with Trichosurus eliminated instead, the Wallabia-Macropus group was recovered. Only analysis of the eleven ingroup taxa by themselves gave a topology which supported both major clades. Our findings suggest that, at least for DNA hybridization studies, when ingroup taxa are separated by very short internodes experimental error in outgroup-to-ingroup distances may seriously compromise determination of ingroup affinities as well as the position of the root. We recommend that in such cases separate analyses with the outgroups sequentially eliminated and rigorous validation of the topology at each step should be conducted.

Divergence in cuticular hydrocarbons between parapatric subspecies of the meadow grasshopper,chorthippus parallelus(Orthoptera, Acrididae)

Abstract: Two subspecies of the grasshopper Chorthippus parallelus (Orthoptera; Acrididae) meet and form a hybrid zone in the Pyrenees. Here we investigate whether the subspecies differ in the blend of cuticular hydrocarbons. Such differences may function as chemical signals, being detected via contact chemoreception and used during mate choice as in other insects. Gas chromatography shows that the subspecies have diverged in the composition of their cuticular hydrocarbons. This difference between subspecies exists over and above variation in cuticular hydrocarbons among individual populations. The majority of the difference can be attributed to the relative amounts of a small group of compounds present in the cuticle. The possible consequences of this chemical divergence for mating encounters between the subspecies are discussed.