Showing papers in "Diversity and Distributions in 2000"

Naturalization and invasion of alien plants: concepts and definitions

Abstract: . Much confusion exists in the English-language literature on plant invasions concerning the terms ‘naturalized’ and ‘invasive’ and their associated concepts. Several authors have used these terms in proposing schemes for conceptualizing the sequence of events from introduction to invasion, but often imprecisely, erroneously or in contradictory ways. This greatly complicates the formulation of robust generalizations in invasion ecology. Based on an extensive and critical survey of the literature we defined a minimum set of key terms related to a graphic scheme which conceptualizes the naturalization/invasion process. Introduction means that the plant (or its propagule) has been transported by humans across a major geographical barrier. Naturalization starts when abiotic and biotic barriers to survival are surmounted and when various barriers to regular reproduction are overcome. Invasion further requires that introduced plants produce reproductive offspring in areas distant from sites of introduction (approximate scales: > 100 m over 6 m/3 years for taxa spreading by roots, rhizomes, stolons or creeping stems). Taxa that can cope with the abiotic environment and biota in the general area may invade disturbed, seminatural communities. Invasion of successionally mature, undisturbed communities usually requires that the alien taxon overcomes a different category of barriers. We propose that the term ‘invasive’ should be used without any inference to environmental or economic impact. Terms like ‘pests’ and ‘weeds’ are suitable labels for the 50–80% of invaders that have harmful effects. About 10% of invasive plants that change the character, condition, form, or nature of ecosystems over substantial areas may be termed ‘transformers’.

Interference interactions, co-existence and conservation of mammalian carnivores

Abstract: The shift in emphasis from single spe- cies to ecosystem conservation is revealing how community interactions can potentially influence single species viability and conservation. Although there is much theory and empirical data concerning the dynamic consequences of exploitative inter- actions, there is still a very poor understanding of the effects of interference interactions. Recent studies, as shown in this review, have documented widespread effects of such interactions among mammalian carnivores. Harassment, loss of kills and intraguild predation have been documented in a wide range of species. The demonstrated effects also include avoidance of larger carnivores in both time and space and reductions in one species density or even total exclusion from certain habitats or regions. Our review of the literature thus provides a range of empirical examples that together demonstrate that these interactions have very important implications on carnivore demography. We believe that the effects of interference might differ strongly from the effects of exploitative competition. This is because interference might have the potential to affect population growth in an inverse density- dependent manner and thereby also reduce popu- lation growth at low densities, therefore increasing extinction probabilities. These factors need to be considered when planning future multi-species con- servation. Further research into the temporal and spatial aspects of co-existence are required if diverse guilds and communities are to be conserved.

Track analysis and conservation priorities in the cloud forests of Hidalgo, Mexico

Abstract: A track analysis based on the distribu- tional patterns of 967 species of vascular plant taxa (gymnosperms, angiosperms and pteridophytes) was performed to assess conservation priorities for cloud forests in the state of Hidalgo, Mexico, ranged in the municipalities of Chapulhuacan, Eloxochitlan, Molocotlan, Pisaflores, Tenango de Doria, Tlahuelompa and Tlanchinol, as well as five floristically equivalent areas in the states of Veracruz (Teocelo and Helechales), Tamaulipas (Gomez Farias), Morelos-Mexico (Ocuilan) and Oaxaca (Huautla de Jimenez). In order to detect generalized tracks we employed a new parsimony method, where clades (considered equivalent to generalized tracks) are defined forbidding homoplasy and acting like a compat- ibility algorithm. Several generalized tracks were found connecting these areas. Cloud forests of Chapulhuacan were connected according to three different generalized tracks and thus have a higher value, qualifying as a priority area for the conservation of cloud forests in the state of Hidalgo.

Past distribution and ecology of the cork oak (Quercus suber) in the Iberian Peninsula: a pollen-analytical approach

Abstract: This study presents pollen-analytical data from continental and offshore Iberian Peninsula sites that include pollen curves of Quercus suber, to provide information on the past distribution and ecology of the cork oak (Q. suber). Results centre on a new pollen record of Navarres (Valencia, eastern Spain), which shows that the cork oak survived regionally during the Upper Pleistocene and was important during a mid-Holocene replacement of a local pine forest by Quercus-dominated communities. This phenomenon appears linked to the recurrence of fire and reinforces the value of the cork oak for reforestation programmes in fire-prone areas. In addition to Navarres, other Late Quaternary pollen sequences (Sobrestany, Casablanca- Almenara, Padul, SU 8103, SU8113, 8057B) suggest last glacial survival of the cork oak in southern and coastal areas of the Peninsula and North Africa. Important developments also occur from the Late Glacial to the middle Holocene, not only in the west but also in the eastern Peninsula. It is suggested that, in the absence of human influence, Q. suber would develop in non-monospecific forests, sharing the arboreal stratum both with other sclerophyllous and deciduous Quercus and Pinus species.

The renowned cactus moth, Cactoblastis cactorum: its natural history and threat to native Opuntia floras in Mexico and the United States of America

Abstract: The cactus moth, Cactoblastis cactorumn (Berg) (Phycitidae) is native to South America. It was released as a biological control agent against alien Opuntia-cacti in Australia in the 1920s, then in southern Africa, and latterly on several islands, including those in the Caribbean. In 1989, the cactus moth was discovered in Florida, in the United States of America, where it is now threatening the survival of indigenous Opuntia species. In this paper we identify some of the attributes that have contributed to the success of C cactorumn as a weed biological control agent. Many of these same qualities account for the problems that C cactorum has caused in Florida and pre- dispose it as a major threat to the speciose, native Opuntia-floras of Central and North America. An estimated 79 platyopuntia (prickly pear) species are at risk: 51 species endemic to Mexico; nine species endemic to the United States; and 19 spe- cies common to both countries. Many cultivated and wild Opuntia species, that are used in various ways, are also vulnerable to attack by C cactorurm, including at least 25 species in Mexico and three species in the United States, particularly the widely exploited and culturally important cultivars of 0. ficus-indica. Some control strategies are sug- gested that may minimize the risk and consequences of invasion by the cactus moth. The wider implica- tions of this threat to the practice of weed bio- logical control and to conservation are discussed.

Patterns and trends in the discovery of new Neotropical mammals

Abstract: . Each year new mammalian taxa are described from the Neotropics but, contrary to conventional wisdom, these are not solely rats and bats. Since the publication of the last world checklist in 1992, new species and genera have been described from six orders (Didelphimorphia, Paucituberculata, Insectivora, Chiroptera, Primates and Rodentia) and from all South American countries except Guyana, Bolivia and Paraguay. Names and bibliographic references are listed for seven new genera and 57 new species of Neotropical mammals, representing an average of one new genus and eight new species annually. Each year, systematists revalidate an even greater number of names that were previously thought to constitute taxonomic synonyms. Consequently, estimates of mammalian diversity remain imprecise, especially in the tropics, and the pace of new descriptions outstrips even the most recent checklists.

The distribution and prevalence of sponges in relation to environmental gradients within a temperate sea lough : inclined cliff surfaces

Abstract: . The prevalence and distribution of sponges was surveyed on vertical cliff surfaces at Lough Hyne Marine Nature Reserve, Co. Cork, Ireland. The number of sponge species was recorded at 6-metre depth intervals at four sites within Lough Hyne, and at one site on the adjacent Atlantic coastline to examine differences in abundance and zonation patterns. Sites ranged from an exposed turbulent regime to sheltered, sedimented environments. Individual species showed different distributions and prevalence between sites and with increasing depth. Greatest differences were observed between the most- and least-disturbed sites. Distinct sponge zonation patterns were evident at all sites sampled. Twenty-five species were considered dominant at all five sites with the remaining 48 species considered rare. Only four of the 25 most-dominant species occurred at the site experiencing the most turbulent flow conditions, whereas 12 species were found at the site of unidirectional fast flow. At sites of moderate to slight water movement and high sedimentation, between 18 and 24 of the most dominant species were present. Encrusting forms constituted high proportions of sponge communities at all five sites sampled (although consisting of different species). At sites of turbulent and unidirectional fast flow massive forms also dominated whereas at the least turbulent sites, where sedimentation was high, arborescent sponges were abundant. Few species showed exclusive distribution to a single depth and site, but there was some degree of correlation between species distributions and abiotic factors such as sedimentation rate and flow regimes. Sponge distributions and densities are discussed with respect to the suitability of species’ morphologies to particular environments, intra-specific and inter-specific competition and physiological adaptations that enable them to survive in different habitats.

Alpha diversity of lianas in a tropical evergreen forest in the Anamalais,Western Ghats, India

Abstract: Species richness, abundance, size-class distribution, climbing mode and spatial patterns of lianas were investigated in a 30-ha perman- ent plot of tropical evergreen forest at Varagalaiar in the Anamalais, Western Ghats, India. Each hectare was subdivided into 10 m x 1O m quad- rats, in which all lianas 2 1 cm d.b.h. were meas- ured, tagged and identified. The total liana density was 11, 200 individuals (373 ha-1) and species richness was 75 species, representing 66 genera and 37 families. The richness estimators employed for species and family accumulation curves after 100 times randomization of sample order, have stabilized the curves at 16th and 15th hectares, respectively. A greater proportion of lianas was twiners (55% of species and 44.4% of density) and root climbers (5% of species and 14% of density), and a few were tendril climbers, reflecting the late successional stage of the forest. In the size-class distribution, 82% of abundance and 97% of species richness fell within 1-3 cm diameter threshold. The dominance of succulent diaspore type signifies the faunal dependence of lianas on vertebrate frugivores for dispersal. The diversity, population density and family composition of lianas of our site is compared with those of other tropical forests. The need for biomonitoring of this synusia in the permanent plot for forest functioning is emphasized.

Feeding and breeding across host plants within a locality by the widespread thrips Frankliniella schultzei, and the invasive potential of polyphagous herbivores

Abstract: Polyphagous insect herbivores could be expected to perform relatively well in new areas because of their ability to exploit alternative resources. We investigated relative abundance patterns of the polyphagous thrips species Frankliniella schultzei, which is characteristically found on plants from many different families, to establish the role of different host plant species in a single locality where the species is not indigenous (Brisbane, south-eastern Queensland, Australia). F. schultzei females and larvae were always present in flowers (where oviposition takes place) and never on leaves of the eight plant species that we surveyed regularly over one year. They were present in flowers of Malvaviscus arboreus in much higher densities than for any other host. F. schultzei females were more fecund and larvae developed faster on floral tissue diets of M. arboreus than on those of other hosts. M. arboreus is therefore regarded as the 'primary' host plant of F. schultzei in the locality that we investigated. The other species are regarded as 'minor' hosts. Available evidence indicates a common geographical origin of F. schultzei and M. arboreus. F. schultzei may therefore be primarily adapted to M. arboreus. The flowers of the minor species on which F. schultzei is also found may coincidentally share some features of the primary host. Adult thrips may therefore accumulate on minor hosts and breed there, but to a lesser extent than on the primary host. The general implications for investigating polyphagous host relationships and interpreting the ecology of these species as generalist invaders are spelt out.

The impact of the invasive alien grass Cortaderia jubata (Lemoine) Stapf on an endangered mediterranean‐type shrubland in California

Abstract: Since its introduction in the late 1800s, the perennial tussock grass Cortaderia jubata (Lemoine) Stapf has become an increasingly fre- quent member of coastal plant communities in California and Oregon. In this study, the com- munity changes associated with C. jubata inva- sion into the mediterranean-type vegetation of Vandenberg Air Force Base, California were exam- ined. Pristine plots of maritime chaparral were compared with spatially and topographically matched plots dominated by C. jubata . Aerial photo- graphs indicated that the invaded plots had previ- ously been shrubland. C. jubata invasion created a structurally less complex perennial grassland that was markedly depauperate in native shrub species. The absence of native shrubs depressed native richness in jubata grassland, but the greater rich- ness of both native and alien herbaceous spe- cies made overall richness in jubata grassland indistinguishable from maritime chaparral. Vegeta- tional differences were associated with differences in arthropod and small mammal populations be- tween vegetation types. Arthropod abundance and order diversity were lower in plots dominated by C. jubata than in adjacent chaparral. Insect traps in C. jubata plots contained a significantly smaller proportion of Hymenoptera and Homoptera and a significantly greater proportion of Araneae than traps in maritime chaparral. Rodent activ- ity was significantly lower while rabbit activity was significantly greater in jubata grassland com- pared to maritime chaparral. This study indicates that the presence of C. jubata can dramatically alter the mediterranean-type landscape of central California. While it is likely that the initial establish- ment of C. jubata is associated with disturbances that are common in this ecosystem, the ability of C. jubata to expand from founding populations and to persist for long periods of time pose a seri- ous threat to the native diversity of these unique systems.

Thrushes now largely restricted to the built environment in eastern England.

Abstract: . I studied the distribution and density of three thrush populations, blackbird Turdus merula, song thrush T. philomelos and mistle thrush T. viscivorus, in an urban and contiguous rural area, totalling 2636 ha, in eastern England. Populations of these species are declining and I found 826, 85 and 30 territories of blackbird, song thrush and mistle thrush, respectively. Significantly more territories of all species than expected were within the urban boundary. Significantly more territories than expected were found of all three species in the built environment (residential housing, factories, schools, etc. with their associated gardens and green-space), urban and rural areas combined. Farmland occupied 67% of the study area but held significantly fewer blackbird and mistle thrush territories than expected, associated mainly with the small amount of grass; song thrushes were not recorded on farmland. Rural woodland and scrub held more blackbird and song thrush territories than expected. Song thrush was significantly associated with scrub within the urban boundary. With all three species largely absent from farmland, residential habitats can be considered as habitat refuges. The consequences of this for conservation and planning are discussed.

Species richness of marine Bryozoa in the continental shelf and slope off Argentina (south-west Atlantic)

Abstract: Fil: Lopez Gappa, Juan Jose. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina

National‐scale conservation assessments at an appropriate resolution

Abstract: Most national-scale conservation assess- ments are carried out at a resolution that is differ- ent from the actual size of protected areas in the study region. Coincidence between nature reserves and both hotspots (areas of high spe- cies richness) and complementary areas (sets of sites within which all species are represented) have been reported. However, the resolution (size of grid cells) of the species' distribution data upon which many of these studies are based is often close to an order of magnitude larger than the size of the reserves. Presumably, only a propor- tion of the species recorded in the coarse grid cells will actually be present on reserves. We use fine (2 x 2-km square grid cells) and coarse (10 x 10-km square grid cells) resolution data of national distributions for breeding birds through- out Great Britain, and presence data for avian species on Royal Society for the Protection of Birds (RSPB) nature reserves, to investigate the proportion of species in the local area (100 km2) that are actually present on reserves. RSPB reserves contain between 50% and 70% of spe- cies from the local area. These proportions are significantly higher than for randomly selected, non-reserve areas, indicating that RSPB reserves contain higher concentrations of bird species than the wider countryside. Furthermore, on RSPB reserves these proportions of threatened and non-threatened species are equal, whereas in non- reserve areas the proportions of non-threatened species are significantly higher than threatened species. Thus, reserves hold a higher proportion of threatened species than occurs in the wider countryside.

Climatic and spatial patterns of diversity in the serpentine plants of California

Abstract: . The insular distribution of distinctive substrates, such as outcrops of serpentine rock, may either promote plant diversity by enhancing opportunities for speciation or reduce diversity by increasing rates of extinction. To examine the relationship between diversity and the spatial structure of habitats, we studied large-scale patterns of diversity in the flora of serpentine in California. We used multiple linear regressions on geographical information system (GIS)-derived data for 85 subregions of the state to analyse the climatic and spatial correlates of plant species richness. The diversity of plants endemic to serpentine declined from north to south and from the coast inland, in association with decreasing rainfall; the same trends were seen in the total flora, but the trends were stronger in serpentine endemics. Diversity of serpentine endemics increased with the area of serpentine and decreased with the mean isolation of serpentine patches in a subregion. The diversity of endemics was not correlated with the number of serpentine patches or their mean perimeter-to-area ratio. We conclude that patchiness in this terrestrial habitat does not appear to promote diversity, even at the large spatial scale associated with speciation and endemism.

Grasshopper (Orthoptera : Acridoidea) species diversity in the Pampas, Argentina

Abstract: . A study was conducted to describe the major features of geographical and temporal variation in the diversity of grassland grasshopper species (Orthoptera: Acridoidea) in different sites of the Pampas, Argentina. Species richness and relative abundance were assessed at 12 sites in eastern La Pampa and western Buenos Aires provinces, from 1994 through 1999. Mean species richness at the regional level was 10, and 34 grasshopper species were collected throughout of the study. Comparison with grasshopper species diversity from the Great Plains of North America is discussed. An evaluation of the proportions of species in each of the three distribution groups (broad, intermediate and narrow) revealed that, over all sites, broadly distributed species made up 14.7% of species composition and intermediately and narrowly distributed species made up 26.5% and 58.8%, respectively. The three top-ranked species in the studied sites were Dichroplus elongatus, D. pratensis and Staurorhectus longicornis. Results showed that, contrary to what was expected, one of the widely distributed species in the region (i.e. Baeacris punctulatus) does not always constitute one of the most abundant species. Finally, the loss of one of the historically most common species in the Pampas, D. maculipennis, is also discussed.

Compost heaps — refuges and stepping‐stones for alien arthropod species in northern Europe

Abstract: . Compost heaps house a species-rich fauna of arthropods. This survey reviews changes in the composition of the beetle fauna in compost heaps in the Nordic countries during the 20th century. A total of 34 alien beetle species have established in compost heaps; 12 of these are also established in natural habitats. A combination of long-distance human transport and short-distance natural spread are proposed as dominant factors, explaining the dispersal of the species. An eastern route of immigration is proposed for Baeocrara japonica, Lithocharis nigriceps, Bohemiella paradoxa, Acrotona pseudotenera and Oxytelus migrator, while a southern route of immigration is proposed for Perigona nigriceps, Acrotona parens, Falagrioma concinna, Trichiusa immigrata, Cartodere nodifer, Ahasverus advena, Oryctes nasicornis and Atheta triangulum. There is no relationship between the types of compost preferred by the different species and the dominant way of dispersal. Among the trophic guilds that species belong to, the predators are more dependent on human transport than natural dispersal. The trophic guild to which a species belongs has no effect on whether or not the species is established away from compost heaps. The generalized compost fauna and species associated with bark compost naturalize away from compost heaps more successfully than expected. It is hypothesized that the successful establishment of alien species in compost habitats results from increased frequency of introductions and warm, thermal stability in large compost heaps during the Nordic winter. The establishment of new species in compost habitats probably has a minor impact on native inhabitants.

The effect of short fire cycles on the cover and density of understorey sprouting species in South African mountain fynbos

Abstract: . Two South African mountain fynbos sites were studied to determine the effect of short fire cycles on the cover and density of understorey sprouting species and their subsequent effect on plant-species richness. Frequent fires (4–6 years between burns) increased the cover of sprouting species by 32% when compared to an adjacent site where the penultimate fire was 28 years previously. There was little or no effect of fire frequency on the densities of understorey sprouters; however, individuals were larger at sites with short fire cycles. The response of individual species of sprouters was variable with one species, Hypodiscus striatus, showing no response to fire frequency. The impact of sprouting species on the species richness of the plant community was great. The mean number of species recorded in quadrats with a high cover of sprouters was 60% lower in comparison to quadrats with low covers or under the burned skeletons of overstorey proteas. The effect of sprouters was consistent for all functional groups of species (i.e. sprouters, non-sprouters, short-lived and long-lived species), in each case reducing the number of species present.

Biogeographic variation in coral species diversity on coral reefs in three regions of Indonesia

Abstract: This paper assesses variation in coral species diversity within the Indonesian archipelago, and the influence of regional species pools, geo- morphology and anthropogenic pollution on coral species diversity and occurrence. We obtained transects from 33 sites on 14 reefs in three regions of Indonesia: Ambon (Moluccas), South Sulawesi and the Java Sea. We determined the within-site species richness by using species- sampling curves. Cluster analysis and multi- dimensional scaling showed that land-based pollution was the primary determinant of coral species diversity and species occurrence on reefs. Relatively unaffected reference sites in eastern Indonesia were approximately 20% more diverse than Java Sea reference sites. Rare species formed a higher proportion of the coral fauna on east- ern Indonesian sites, and eastern Indonesian apparent endemic species contributed approx- imately 25% of the total species pool sampled. Between-site variation in species occurrence was lower on Java Sea reefs than on eastern Indonesian reefs. A larger species pool in eastern Indonesia than in the Java Sea probably accounted for most of the difference in within-site spe- cies diversity between eastern Indonesian and Java Sea reference sites. High fishing intensity in the Java Sea, including destructive fishing practices, may have also contributed to reduced within- site species diversity on Java Sea reference reefs. Despite the fact that the Java Sea was exposed during Pleistocene lowstands, and was recolon- ized by marine organisms only within the last 10 000 years, coral species diversity and assem- blage composition on the Java Sea reefs was largely similar to open ocean reefs in eastern Indonesia.

Deficit in community species richness as explained by area and isolation of sites

Abstract: . The potential community species rich-ness was predicted for 85 patches of seminaturalgrassland in an agricultural landscape in Denmark.The basis of the prediction was a very large data-set on the vegetation, soil pH and topographyin Danish grasslands and related communities.Species were inserted into potential species poolsaccording to their preferences regarding soil acidityand water availability (expressed as potential solarirradiation), and to the ranges in these two factorsobserved in each grassland patch. The differencebetween the predicted and the observed patch-level species richness, community richness deficit,varied considerably among patches. Communityrichness deficit exhibited a negative relationshipwith patch area, and for small patches a positiverelationship with patch isolation. Key words. Assembly rules, isolation, patch area,species pool, temperate grassland. INTRODUCTION It has been shown repeatedly that area, isola-tion and habitat heterogeneity are the majordeterminants of species richness in habitat islands(for temperate grasslands, e.g. Simberloff & Gotelli,1984; Eriksson

Competitive interactions between overstorey proteas and sprouting understorey species in South African mountain fynbos

Abstract: . Previous studies in the mountain fynbos of South Africa have demonstrated that short fire cycles favour the establishment of dense covers of understorey sprouters while longer fire intervals enable the establishment from seed of overstorey proteas and the formation of a overstorey. One consequence of these differences between fire cycle lengths is the effect that understorey sprouters and an overstorey protea canopy have on species richness. In the case of short fire intervals, species richness is decreased while longer intervals between fires allow species richness to decrease or increase depending on the patchiness of the overstorey canopy. Such results are suggestive of competitive effects between understorey sprouters and overstorey canopy proteas. In this study, data were collected from several pyric successional stages in mountain fynbos to study the effect of overstorey proteas on the growth and flowering of understorey sprouters since the last fire. Data were also collected to determine the effect that understorey sprouters had on the establishment and fecundity of overstorey protea species. Competitive interactions between overstorey proteas and sprouting understorey species were evident at all the sites studied. The vegetative growth and seed production of understorey sprouters, which grew under a canopy of overstorey proteas during the current interfire period, were significantly lower than that for plants growing in the open. In addition, the postfire growth and seed production of understorey sprouters were significantly lower for individuals, which grew under an overstorey protea canopy during the previous fire cycle, than for those individuals which grew in the open. The fecundity of overstorey proteas, which grew near understorey sprouters, was lower than that of plants which grew in the open. This effect was evident for up to the first 15 years after a fire. However, not all understorey sprouters affected the overstorey proteas equally. Also, seedlings of overstorey proteas established significantly less successfully in close proximity to understorey sprouters after a fire than in the open or under proteas. Finally, the results demonstrate that complex species-specific, understorey–overstorey interactions are important in mountain fynbos. For example, some overstorey species depend on trophically similar species to reduce potential competition from understorey sprouters for their successful establishment at a site.

Allozyme diversity and geographic variation in the widespread coastal sedge, Carex arenaria

Abstract: Allozyme electrophoresis was used to investigate the structure of genetic variation in the rhizomatous coastal sedge, Carex arenaria, throughout its European range — from the SW Iberian peninsula to the Baltic region. Material was sampled from 77 sites in five geographic regions. Nine of the 13 investigated loci were polymorphic in the total material and there were interregional differences in the number of polymorphic loci per site and the percentage of variable sites. In the Scandinavia/Baltic region only 61% of the sites contained at least one locus with more than one allele, whereas all the British and SW Iberian sites were variable. There was a general tendency for the regional frequencies of the less common alleles at individual loci to decline from SW to NE. The mean (over loci and sites) within-site gene diversity (H ¯site) was 0.064 (in calculations based on the number of observed multilocus allozyme genotypes within each sampling site). Although there was considerable variation between geographically adjacent sites, within-site diversity showed a general decrease from SW to NE in Europe. There were significant differences in within-region gene diversity (Hreg) for the four most variable loci between the five regions. Hreg generally decreased from SW to NE Europe and most loci showed the highest diversity in the SW Iberian peninsula and the Bay of Biscay regions. The mean (over loci) gene diversity in the total material (Htot) was 0.070 and the levels of diversity in Carex arenaria are substantially lower than is usual in rhizomatous sedges. The within-site, between-site and between-regional components of the total diversity were 92.4%, 2.5% and 5.1%, respectively. The low levels of overall gene diversity in C. arenaria and the successive decrease in diversity from SW to NE are interpreted in terms of the species' history of postglacial spread into northern Europe. Despite the overall northwards decrease in diversity, the widespread occurrence of less common alleles and the lack of regional deviations from Hardy–Weinberg genotype frequency expectations suggest that C. arenaria is not predominantly self-fertilized. (Less)

Typological thinking and the conservation of subspecies: the case of the San Clemente Island loggerhead shrike

Abstract: Hybridization with closely related taxa poses a significant threat to endangered sub- species (e.g. outbreeding depression, inbreeding) and confounds efforts to manage and conserve these taxa through a loss of taxonomic identity, in part because of the practical necessity of defining subspecies in a typological manner. We examined nine morphological characters in 167 post-juvenile museum specimens to deter- mine if loggerhead shrikes Lanitis ludoviciantis Linnaeus 1766 on San Clemente Island (off the coast of California) remain diagnosable as L. 1. niearnsi Ridgway (1903); an island endemic listed as endangered by the United States Fish and Wildlife Service. Four recent shrike speci- mens from the island were compared to histor- ical specimens using a bivariate scatter plot and a discriminant function (the latter was used to clas- sify recent specimens post hoc). The few recent specimens were not diagnosable as L. 1. mearnsi, but instead appear to be intergrades between L. 1. mearnsi and L. 1. anthonyi Mearns 1898 (the subspecies endemic to Santa Cruz, Santa Catalina, Santa Rosa and Anacapa islands), and are per- haps closer to pure antlhonyi. Our data and the species' natural histoiy and distribution suggest that shrikes currently on San Clemente Island are the result of genetic 'swamping' of inearuasi by anthonyi. Under a necessarily typological defini- tion of a subspecies, it is evident that inearnsi is probably no longer diagnosable. Howevei; we conclude that protection of the entire Channel Islands population of the loggerhead shrike would be the best management strategy, as the species has declined drastically throughout the islands.