Contrasting Genetic Structure in Two Co-Distributed Species of Old World Fruit Bat

The fulvous fruit bat (Rousettus leschenaulti) and the greater short-nosed fruit bat (Cynopterus sphinx) are two abundant and widely co-distributed Old World fruit bats in Southeast and East Asia. The former species forms large colonies in caves while the latter roots in small groups in trees. To test whether these differences in social organization and roosting ecology are associated with contrasting patterns of gene flow, we used mtDNA and nuclear loci to characterize population genetic subdivision and phylogeographic histories in both species sampled from China, Vietnam and India. Our analyses from R. leschenaulti using both types of marker revealed little evidence of genetic structure across the study region. On the other hand, C. sphinx showed significant genetic mtDNA differentiation between the samples from India compared with China and Vietnam, as well as greater structuring of microsatellite genotypes within China. Demographic analyses indicated signatures of past rapid population expansion in both taxa, with more recent demographic growth in C. sphinx. Therefore, the relative genetic homogeneity in R. leschenaulti is unlikely to reflect past events. Instead we suggest that the absence of substructure in R. leschenaulti is a consequence of higher levels of gene flow among colonies, and that greater vagility in this species is an adaptation associated with cave roosting

The evolution of sociality in small, carnivorous marsupials: The lek hypothesis revisited

One of the few mammal species reported to have a mating system of lek promiscuity is the tree-hollow nesting marsupial, the agile antechinus, Antechinus agilis. Past conclusions about its mating system have been based on seasonal changes in social group size, sex-specific nest switching and space use. Thermoregulation has also been suggested as an explanation for variation in social behaviour in this species and its relatives. We tested predictions of the lekking and thermoregulation hypotheses to explain sociality in cavity nesting antechinuses using published data, and new data on brown and subtropical antechinuses. We found that across four species, social group size is negatively correlated with daily minimum temperature, but not with timing of breeding. Females have a matrilineal fission-fusion social system, which continues during the brief mating season, and males range increasingly further throughout their lives, contacting as many females as possible in nests. Males show no indication of fission-fusion sociality. All evidence in species other than A. agilis, and some data on A. agilis, indicate a mating system of scramble polygyny, and not lek promiscuity. We conclude that across species, thermoregulation is the main reason for seasonal variation in nesting group size in both sexes

Les accords-cadre internationaux, un outil de régulation et de management pour les entreprises multinationales ? L'exemple de l'accord EDF

Females in a variety of taxa mate with more than one male during a single oestrus and exhibit mate preferences for genetically compatible males, but the influence of female mate choice on siring success is not clearly understood. Whether females choose to mate with more than one male or endure forced copulations is also often unknown. Here, we examined the effects of genetic relatedness on female mate choice and siring success in a small semelparous carnivorous marsupial, the agile antechinus (Antechinus agilis), during two consecutive breeding seasons. Experimental trials were conducted in captivity over periods of 72 hours using interconnected enclosures in which female antechinus could choose to access any of four separated males, but males were only able to access females that entered their quarters. Females had access to two genetically similar and two genetically dissimilar males simultaneously and all behavioural interactions were observed and scored from continuous video recordings. Genetic similarity between mates and paternity of young was determined by microsatellite analyses. Some females chose to enter and mate with more than one male during a single oestrus period. Although females investigated all males, they spent significantly more time visiting, and mated more times with, genetically dissimilar males. Males that were genetically dissimilar to the female sired 88% of subsequent offspring. Whilst males mated readily with most females, they rejected the advances of some receptive females, indicating a previously unexpected level of male mate choice. The results show that genetic relatedness between mates has a significant influence on mate choice, breeding and siring success in the agile antechinus

Post-mating sexual selection increases lifetime fitness of polyandrous females in the wild

Females often mate with several males before producing offspring(1). Field studies of vertebrates suggest, and laboratory experiments on invertebrates confirm, that even when males provide no material benefits, polyandry can enhance offspring survival(2,3). This enhancement is widely attributed to genetic benefits that arise whenever paternity is biased towards males that sire more viable offspring(1,4,5). Field studies suggest that post-mating sexual selection biases fertilization towards genetically more compatible males(6,7) and one controlled experiment has shown that, when females mate with close kin, polyandry reduces the relative number of inbred offspring(8). Another potential genetic benefit of polyandry is that it increases offspring survival because males with more competitive ejaculates sire more viable offspring(9). Surprisingly, however, there is no unequivocal evidence for this process(10). Here, by experimentally assigning mates to females, we show that polyandry greatly increases offspring survival in the Australian marsupial Antechinus stuartii. DNA profiling shows that males that gain high paternity under sperm competition sire offspring that are more viable. This beneficial effect occurs in both the laboratory and the wild. Crucially, there are no confounding non-genetic maternal effects that could arise if polyandry increases female investment in a particular reproductive event(10) because A. stuartii is effectively semelparous. Our results therefore show that polyandry improves female lifetime fitness in nature. The threefold increase in offspring survival is not negated by a decline in maternal lifespan and is too large to be offset by an equivalent decline in the reproductive performance of surviving offspring

Peramorphic males and extreme sexual dimorphism in Monodelphis dimidiata (Didelphidae)

The southern short-tailed opossum, Monodelphisdimidiata, is a species known not only for its semelparouslife cycle, but also for the extreme sexualdimorphism of adults, where males are not only larger, butalso have distinctive morphological characters in theirskull. Using geometric morphometrics and a suite of statisticaltests, I analyzed the postweaning ontogeneticdevelopment of this species in order to evaluate the ageclasswhere sexual dimorphism becomes significant and theamount of change exhibited by both sexes. My resultsshowed that M. dimidiata partly follows the ontogeneticpattern described for didelphids by previous authors. Thecharacter that escapes the general pattern is rostral length,which becomes shorter instead of lengthening throughoutthe development. This change could be related to anincrement in the bite force in the anterior part of the dentition.The amount of sexual dimorphism found for thisspecies is larger than the reported previously for otherAmerican marsupials, and I also found a higher rate ofgrowth in males at the attaining of sexual maturity. Basedon my results and the information available for otherdidelphids, I can suggest that M. dimidiata males undergothrough a process of hypermorphosis, resulting in aperamorphic condition. It is possible that the extremesexual dimorphism present in this species is related toreproductive success, specially taking into account theirsemelparous life cycle.Fil: Chemisquy, Maria Amelia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin

Use of space by the yellow-footed antechinus, Antechinus flavipes, in a fragmented landscape in South Australia

An understanding of how individual species are able to persist and move within fragmented landscapes is critical for elucidating the effects of fragmentation and aiding in the management of species. Here, we studied movement behaviour of the dasyurid Antechinus flavipes in a heavily fragmented landscape using trapping and radiotracking. We assessed the ability of animals to move within and amongst small (<6 ha) remnants and make use of the matrix, and investigated how females used the available space within remnants. Seventeen between-remnant movements were detected from 428 recaptures, ranging in length from 30 to 720 m and averaging 352 m. Most were by adult males during the breeding season, with 40% more than 500 m. Landscape types traversed would have included exotic pine plantations, open grazed areas and roads. Between-site movements of juveniles were only detected on three occasions. However, few young males were captured as adults, suggesting high dispersal rates and considerable matrix use. Conversely, despite high female recapture rates, again only three between-site movements were recorded. Radiotracking further indicated that females confined foraging to remnants, with occasional forays to isolated trees in paddocks. Female home range areas were similar for remnants and forest (0.04-0.66 ha). A. flavipes is clearly able to persist in very small patches of native vegetation in the landscape studied here. Its long-term persistence appears dependent on the ability of females to maintain a presence in the small remnants, and of unrelated males to move between remnants to breed with resident females. This study illustrates the importance of recognising the occurrence of metapopulations in fragmented landscapes for conservation management. © 2008 Springer Science+Business Media B.V.Doreen Marchesan and Susan M. Carthe