Molly A. Whalen

Bio: Molly A. Whalen is an academic researcher from Flinders University. The author has contributed to research in topics: Systematics & Nectar. The author has an hindex of 12, co-authored 36 publications receiving 396 citations. Previous affiliations of Molly A. Whalen include University of California, Berkeley.

Patterns of ant and herbivore activity on five understory euphorbiaceous saplings in submontane Papua New Guinea

Abstract: We present the results of a study of the ant and herbivore faunas found on the leaves of five species of euphorbiaceous saplings (Macaranga aleuritoides, M. punctata, M. quadriglandulosa, Mallotus philippensis, and Homalanthus novo-guineensis) during the wet season in a submontane tropical rain forest in Papua New Guinea. All of these species have foliar extrafloral nectaries. The abundance, density, and composition of the ant and herbivore communities differed among the tree species; ant densities per unit leaf area varied by a factor of ca 20; and herbivore densities varied by a factor of ca 3. The leaves of these species were visited by 6 to 13 species of ants. Ants were experimentally excluded from branches or small saplings of three tree species: Macaranga aleuritoides, M. punctata, and Homolanthus novo-guineensis. Numbers of herbivores and levels of leaf damage were found to be significantly greater on ant exclusion saplings than on ant access saplings for M. aleuritoides, but not for the other two species. Macaranga aleuritoides was visited by more ant species than the other four tree species and had the highest number of ants per leaf. The antplant associations we examined are relatively unspecialized compared with most of the ant associations with euphorbs that have been studied previously in the Indo-Malesian tropics. MANY PLANTS POSSESS EXTRAFLORAL NECTARIES (EFNs) that are visited by ants, and the role of ants in defending such plants from herbivory has been examined in a number of experimental studies (e.g., Koptur 1979, 1984; O'Dowd 1979; Schemske 1982; Stephenson 1982; Horvitz & Schemske 1984). Several of these studies have shown that ants can indeed protect plants from herbivores, but in others no such effect has been discerned (O'Dowd & Catchpole 1983, Tempel 1983, Boecklen 1984). This apparent variation in the efficacy of EFNs as defenses against herbivory has led some authors to conclude that the likelihood of a strong mutualistic interaction evolving between ants and plants is affected both by features of the plant (such as growth form and characteristics of the nectaries and nectar) and by temporal and spatial variation in the density and composition of the ant and herbivore fauna visiting the plant (e.g., Boecklen 1984, Horvitz & Schemske 1984, Barton 1986). However, very few data are available concerning this variation, particularly from ant-plant systems in the Indo-Malesian tropics. We present the results of a short-term investigation of the ant and herbivore fauna found on the leaves of five species of euphorbiaceous saplings [Macaranga aleuritoides F. Muell., M. punctata Schum., M. quadriglandulosa Warb., Mallotus philippensis (Lam.) Muell. Arg., and Homolanthus novo-guineensis (Warb.) Schum.} in the understory of a submontane tropical rain forest in Papua New Guinea. All five species have glands on the leaves near the petiole insertion, and our study was prompted by our observations of ants foraging at these glands on all species. In the Indo-Malesian tropics, species in the euphorbiaceous genera we examined show a range of associations with ants. Most previous work on these associations has been done on such species as Macaranga triloba that provide specialized food bodies and/or nest sites for one or a few species of attendant ants (e.g., Ridley 1910, Rickson 1980, Maschwitz et al. 1984); very little experimental work has been done on species that have EFNs but do not show highly specialized relationships with one or a few ant species. We attempted to determine the differences, if any, between the ant and herbivore communities on the leaves of the five tree species, and examine the consequences, in terms of herbivore numbers and herbivory, of excluding ants from leaves with active

Systematics of the Rubus fruticosus aggregate (Rosaceae) and other exotic Rubus taxa in Australia

Abstract: Exotic Rubus taxa in Australia have been revised following consultation with European and North American experts in Rubus, allied with studies of variation in patterns of DNA restriction fragments and morphology. Many of these taxa have names that are applied for the first time in Australia (prefaced with a †). The major focus of the work was the Rubus fruticosus L. aggregate and taxa of this aggregate covered here are R. anglocandicans A. Newton, R. cissburiensis W.C. Barton & Ridd., †R. echinatus Lindl., †R. erythrops Edees & A. Newton, R. laciniatus Willd., R. leightonii Lees ex Leight. †R. leucostachys Schleich. ex Sm., †R. phaeocarpus W.C.R. Watson, R. polyanthemus Lindeb., †R. riddelsdellii Rilstone, †R. rubritinctus W.C.R. Watson, R. ulmifolius Schott (including R. ulmifolius var. ulmifolius and †R. ulmifolius var. anoplothyrsus Sudre), and R. vestitus Weihe, along with two undescribed taxa, Rubus sp. Scott Creek (D.E. Symon 16504) and Rubus sp. Tasmania (J.R. Hosking 1551). Other naturalised taxa are R. alceifolius Poir., R. ellipticus Sm., R. idaeus L., †R. laudatus A. Berger, †R. loganobaccus L.H. Bailey, †R. philadelphicus Blanch., R. roribaccus (L.H. Bailey) Rydb. and R. rugosus Sm. Patterns of morphological and molecular variation among individuals of the R. fruticosus agg. in Australia were examined. In phenetic analyses based on examination of 137 herbarium specimens and 27 morphological characters, taxa showed varying degrees of separation. Some taxa, for example R. anglocandicans and the two varieties of R. ulmifolius, formed distinct groups in these analyses whereas there was considerable overlap among individuals of other species. Fifty M13/HaeIII DNA-banding patterns (phenotypes) were identified among 198 collections from the R. fruticosus agg. across Australia. Thirty-five DNA phenotypes were correlated with 15 taxa of the R. fruticosus agg.; the remaining 15 DNA types correlated poorly or were determined with only a moderate level of confidence. R. anglocandicans, R. echinatus, R. leightonii, R. leucostachys, R. sp. Tasmania, R. ulmifolius and R. vestitus had two or more DNA phenotypes whereas only one DNA phenotype was observed for the remaining eight taxa. Taxa that were more distinct with respect to their DNA phenotypes also tended to be more distinct with respect to morphology based on a Mantel matrix correlation test. Within taxa that were difficult to tell apart morphologically, those sharing the same DNA phenotype were considered members of the same Rubus taxon. These results are discussed in the context of the evolution and ecology of the R. fruticosus agg. in Australia and in relation to the incomplete taxonomy of Rubus in Europe and North America.

Seed selection and removal by ants in a tropical savanna woodland in northern Australia

Abstract: Ant species in the genera Chelaner, Meranoplus and Pheidole were found to be seed-harvesters in a tropical savanna woodland in northern Australia. Despite the availability of other seed types (legume seeds in particular were abundant), all five seed-harvesting species studied are specialists in that they store only grass seeds. Depot experiments, in which seeds were placed along foraging trails, also indicate a preference for grass seeds over legume seeds. At least for some ant species the handling efficiency of legume seeds may be less than that of grass seeds. Marked differences in seed composition of granaries were observed among different seed-harvesting ant species and among colonies of the same species at different sites. All ant species studied, except Pheidole sp. 1, stored only one type of grass seed in granaries at any site despite the availability of other seed types. This contrasts with studies conducted elsewhere in Australia in which generalist foraging by seed-harvesters was found to be common. With the possible exception of Pheidole, dietary specialization docs not appear to arise from a low diversity or abundance of seed supplies. In addition to differences in seed preferences, species of seed-harvesting ants also exhibited some differences in temporal foraging behaviour and some partitioning of resources may be occurring among these co-occurring species. Temporal overlap in foraging, however, was much greater than dietary overlap. The viability of granary seeds was very low for three ant species suggesting that seeds stored by these ants were largely predated rather than dispersed.

Aggregated flowering phenologies among three sympatric legumes – The degree of non-randomness and the effect of overlap on fruit set

Abstract: The flowering phenologies of three sympatric legumes, Dillwynia hispida Lindley, D. uncinata (Turcz.)J.Black and Pultenaea densifolia F.Muell. (Fabaceae), were measured over a three-year period in a semi-arid ecosystem. Each species produced a single flowering episode per year which lasted about 15 weeks and which overlapped considerably with those of the remaining two species. A comparison of the actual flowering schedules over two years with those generated from Monte Carlo simulations showed that the flowering schedules of the three species were significantly clumped. Fruit-to-flower ratios on D. hispida plants were calculated over two flowering periods and these values were correlated with conspecific and heterospecific flower abundances to determine whether the extent of overlap in flowering schedules was associated with elevated or depressed levels of fruit set. Partial correlations between heterospecific floral densities and fruit-to-flower ratios were usually positive, indicating a possible selective advantage favouring these convergent flowering schedules.

Multiphase myrmecochory: the roles of different ant species and effects of fire.

Abstract: Seed dispersal by ants (myrmecochory) can be influenced by changes to ant assemblages resulting from habitat disturbance as well as by differences in disperser behaviour. We investigated the effect of habitat disturbance by fire on the dispersal of seeds of a myrmecochorous shrub, Pultenaea daphnoides. We also investigated the consequence of the seed relocation behaviours of two common dispersers (Pheidole sp. A and Rhytidoponera metallica) for the redispersal of seeds. Pheidole sp. A colonies did not relocate seeds outside their nests. In contrast, R. metallica colonies relocated 43.6 % of seeds fed to them, of which 96.9 % had residual elaiosome that remained attached. On average, R. metallica relocated seeds 78.9 and 60.7 cm from the nest entrances in burned and unburned habitat, respectively. Seeds were removed faster in burned than in unburned habitat, and seeds previously relocated by R. metallica were removed at similar rates to seeds with intact elaiosomes, but faster than seeds with detached elaiosomes. Dispersal distances were not significantly different between burned (51.3 cm) and unburned (70.9 cm) habitat or between seeds with different elaiosome conditions. Differences between habitat types in the frequency of seed removal, the shape of the seed dispersal curve, and the relative contribution of R. metallica and Pheidole sp. A to seed dispersal were largely due to the effect of recent fire on the abundance of Pheidole sp. A. Across habitat types, the number of seeds removed from depots and during dispersal trials most strongly related to the combined abundances of R. metallica and Pheidole. Our findings show that myrmecochory can involve more than one dispersal phase and that fire indirectly influences myrmecochory by altering the abundances of seed-dispersing ants.

Trophic cascades in terrestrial systems: a review of the effects of carnivore removals on plants.

Abstract: We present a quantitative synthesis of trophic cascades in terrestrial systems using data from 41 studies, reporting 60 independent tests. The studies covered a wide range of taxa in various terrestrial systems with varying degrees of species diversity. We quantified the average magnitude of direct effects of carnivores on herbivore prey and indirect effects of carnivores on plants. We examined how the effect magnitudes varied with type of carnivores in the study system, food web diversity, and experimental protocol. A metaanalysis of the data revealed that trophic cascades were common among the studies. Exceptions to this general trend did arise. In some cases, trophic cascades were expected not to occur, and they did not. In other cases, the direct effects of carnivores on herbivores were stronger than the indirect effects of carnivores on plants, indicating that top‐down effects attenuated. Top‐down effects usually attenuated whenever plants contained antiherbivore defenses or when herbivore ...

Seed dispersal effectiveness revisited: a conceptual review

Abstract: Growth in seed dispersal studies has been fast-paced since the seed disperser effectiveness (SDE) framework was developed 17 yr ago. Thus, the time is ripe to revisit the framework in light of accumulated new insight. Here, we first present an overview of the framework, how it has been applied, and what we know and do not know. We then introduce the SDE landscape as the two-dimensional representation of the possible combinations of the quantity and the quality of dispersal and with elevational contours representing isoclines of SDE. We discuss the structure of disperser assemblages on such landscapes. Following this we discuss recent advances and ideas in seed dispersal in the context of their impacts on SDE. Finally, we highlight a number of emerging issues that provide insight into SDE. Overall, the SDE framework successfully captures the complexities of seed dispersal. We advocate an expanded use of the term dispersal encompassing the multiple recruitment stages from fruit to adult. While this entails difficulties in estimating SDE, it is a necessary expansion if we are to understand the central relevance of seed dispersal in plant ecology and evolution.

Protective ant-plant interactions as model systems in ecological and evolutionary research.

Abstract: ▪ Abstract Protective ant-plant interactions, important in both temperate and tropical communities, are increasingly used to study a wide range of phenomena of general interest. As antiherbivore defenses “worn on the outside,” they pose fewer barriers to experimentation than do direct (e.g., chemical) plant defenses. This makes them tractable models to study resource allocation to defense and mechanisms regulating it. As multi-trophic level interactions varying in species specificity and impact on fitness of participants, ant-plant-herbivore associations figure prominently in studies of food-web structure and functioning. As horizontally transmitted mutualisms that are vulnerable to parasites and “cheaters,” ant-plant symbioses are studied to probe the evolutionary dynamics of interspecies interactions. These symbioses, products of coevolution between plants and insect societies, offer rich material for studying ant social evolution in novel contexts, in settings where colony limits, resource supply, and ...

Classification and geography of the flowering plants

Abstract: Thome, Robert F. (Rancho Santa Ana Botanic Garden, Claremont, CA 91711). Classification and geography of the flowering plants. Bot. Rev.58(3): 225–348. 1992.—This treatment of the flowering plants is the latest revision of my classification of the Class Angiospermae and replaces my 1983 and more recent 1992 synopses. An update is necessary because so much new information has been published in the last decade pertinent to the classification of the flowering plants. About 870 such recent books, monographs, and other botanical papers are cited in the Introduction, listed primarily by the botanical discipline that they represent. Also considerable changes in my classification have been necessitated by my narrowed family- and ordinal-gap concepts, acceptance of the ending “-anae” for superorders in place of the traditional but inappropriate “-iflorae,” and acceptance of more prior or more widely used names for the categories above the family. A new phyletic “shrub” replaces earlier versions, and attempts to indicate visually relative sizes and relationships among the superorders, orders, and suborders. One table includes a statistical summary of floweringplant taxa: ca. 233,900 species of 12,650 genera, 437 families, and 708 subfamilies and undivided families in 28 superorders, 71 orders, and 71 suborders of Angiospermae. Three other tables summarize the known indigenous distribution of the families and subfamilies of angiosperms about the world. The synopsis lists the flowering plant taxa from the class down to the subfamily (and in Asteraceae down to the tribe) with indication of the degree of confidence I place in the circumscription and placement of each category above the subfamily, the best available estimates of the number of genera and species for each category, and the known indigenous distribution of each subfamily and family. Table V lists alphabetically the geographical abbreviations used in the synopsis. The extensive bibliography of recent literature should be helpful to those persons interested in the classification of the flowering plants.