Abstract: The colonies of ants, bees, wasps and termites, the social insects, consist of large numbers of closely related individuals; circumstances ideal for contagious diseases. Antimicrobial assays of these animals have demonstrated a wide variety of chemical defenses against both bacteria and fungi that can be broadly classified as either external antiseptic compounds or internal immune molecules. Reducing the disease risks inherent in colonies of social insects is also achieved by behaviors, such as multiple mating or dispersal, that lower genetic relatedness both within- and among colonies. The interactions between social insects and their pathogens are complex, as illustrated by some ants that require antimicrobial and behavioral defenses against highly specialized fungi, such as those in the genus Cordyceps that attack larvae and adults and species in the genus Escovopsis that attack their food supplies. Studies of these defenses, especially in ants, have revealed remarkably sophisticated immune systems, including peptides induced by, and specific to, individual bacterial strains. The latter may be the result of the recruitment by the ants of antibiotic-producing bacteria but the extent of such three-way interactions remains unknown. There is strong experimental evidence that the evolution of sociality required dramatic increases in antimicrobial defenses and that microbes have been powerful selective agents. The antimicrobial chemicals and the insect-killing fungi may be useful in medicine and agriculture, respectively.
Abstract: We report on the isolation and characterization of eight microsatellite markers for the coppertail skink (Ctenotus taeniolatus). From a sample of 27 individuals, the number of alleles per locus ranged from seven to 13 and observed and expected heterozygosities ranged from 0.714 to 0.818 and from 0.738 to 0.899, respectively. These loci will be used to assess anthropogenic disturbance on coppertail skink populations. These are the first microsatellites reported for the genus Ctenotus, despite being the most speciose genus of lizards in Australia.
Abstract: Bioprospecting for novel antimicrobials increasingly relies on extremely small samples unsuitable for conventional bulk extraction and assay. We developed a microtitre plate assay for minimal amounts of test materials which is rapid, extremely sensitive, allows time-course analysis and reduces false negatives. Developed for the analyses of antimicrobial sensitivity and resistance, the technique is appropriate for assays where source materials are scarce.
Abstract: Declines in shark populations worldwide are of particular concern to fishery managers and conservation biologists. Molecular-based technologies provide an efficient means to collect basic life-history information and estimates of dispersal that are critical to management. A novel method for obtaining high quality mtDNA from shark jaws and teeth for shark population genetic studies is described. (C) 2008 The Authors Journal compilation (C) 2008 The Fisheries Society of the British Isles.
Abstract: Despite the extensive literature describing the impacts of habitat fragmentation on the distribution and abundance of species, fragmentation effects on life-history strategies have been relatively understudied. Social interactions are important life-history attributes that have fitness consequences for individuals and have been observed to differ among populations in relation to geographic and demographic variability. Therefore, habitat fragmentation is expected to affect social interactions, and these social impacts or responses may contribute to population viability and broad-scale patterns of distribution and abundance in fragmented landscapes. Here we review the emerging literature on this issue. We focus on the impacts of habitat fragmentation that are expected to, or have been observed to, affect social strategies. These include altered resource distribution (e.g., habitat quality, spatial configuration of patches), interspecific interactions (e.g., predator-prey and host-parasite dynamics, human disturbance), and sex (mate availability and inbreeding risk). The studies we cite identified altered social interactions in response to these influences, including changes to home-range overlap, territoriality, group size, and mating systems. The observed changes to social interactions include passive responses, whereby social interactions are affected by constraints introduced by habitat fragmentation, and adaptive social responses to a modified environment. We suggest that future research could focus on individual fitness benefits and on consequences for population viability of altered social interactions in fragmented environments.
Abstract: Fire promotes an abundance of nest sites for the stem nesting bee Exoneura nigrescens, which remain viable for approximately 10 years. The finite duration of nesting substrate and localized fire events suggest that migration should minimize genetic structure among suitable habitat patches. Exoneura nigrescens was sampled from 7 localities with a known fire history in southwestern Victoria, Australia. Individual bees were genotyped at 8 microsatellite loci and genic and genotypic analyses applied to examine genetic structure among burn patch localities, within burn patches, and within colonies. Despite relatively short-term availability of nesting substrates, remarkably fine-scale genetic structure was observed both among burn patches and within burn patches. The spatial distribution of relatedness shows a strong pattern of isolation-by-distance at geographic distances to 35 km, suggesting that genetic partitioning among burn patches is, at least in part, a result of dispersal ability. Genetic structure within burn patches includes colonies consisting of close kin with genic partitioning among nests. Relatedness structure within colonies suggests that polygamy, multiple breeding pairs, and a lack of inbreeding typifies the mating system.
Abstract: We report on the isolation of eight microsatellites from the sand tiger shark, Carcharias taurus, using an enrichment protocol. All loci, with the exception of Cta45-183, were in Hardy-Weinberg equilibrium. Loci exhibited three to 15 alleles, and observed and expected heterozygosities of 0.095-1.000 and 0.284-0.924, respectively. An additional marker (Iox-12) developed from a shortfin mako library was variable in sand tigers. These markers will be used to examine population genetics and mating patterns of this imperilled species.
Abstract: Evidence for the antiquity and importance of microbial pathogens as selective agents is found in the proliferation of antimicrobial defences throughout the animal kingdom. Social insects, typified by crowding and often by low genetic variation, have high probabilities of disease transmission and eusocial Hymenoptera may be particularly vulnerable because of haplodiploidy. Mechanisms they employ to reduce the risk of disease include antimicrobial secretions which are particularly important primary barriers to infection. However, until now, whether or not there is selection for stronger antimicrobial secretions when the risk of disease increases because of sociality has not been tested. Here, we present evidence that the production of progressively stronger antimicrobial compounds was critical to the evolution of sociality in bees. We found that increases in group size and genetic relatedness were strongly correlated with increasing antimicrobial strength. The antimicrobials of even the most primitive semi-social species were an order of magnitude stronger that those of solitary species, suggesting a point of no return, beyond which disease control was essential. Our results suggest that selection by microbial pathogens was critical to the evolution of sociality and required the production of strong, front-line antimicrobial defences.
Abstract: Population numbers of many shark species are declining rapidly around the world. Despite the commercial and conservation significance, little is known on even the most fundamental aspects of their population biology. Data collection that relies on direct observation can be logistically challenging with sharks. Consequently, molecular methods are becoming increasingly important to obtain knowledge that is critical for conservation and management. Here we describe an amplified fragment length polymorphism method that can be applied universally to sharks to identify highly informative genome-wide polymorphisms from 12 primer pairs. We demonstrate the value of our method on 15 divergent shark species within the superorder Galeomorphii, including endangered species which are notorious for low levels of genetic diversity. Both the endangered sand tiger shark (Carcharodon taurus, N = 18) and the great white shark (Carcharodon carcharias, N = 7) displayed relatively high levels of allelic diversity. A total of 59 polymorphic loci (H(e) = 0.373) and 78 polymorphic loci (H(e) = 0.316) were resolved in C. taurus and C. carcharias, respectively. Results from other sharks (e.g., Orectolobus ornatus, Orectolobus sp., and Galeocerdo cuvier) produced remarkably high numbers of polymorphic loci (106, 94, and 86, respectively) from a limited sample size of only 2. A major constraint to obtaining much needed genetic data from sharks is the time-consuming process of developing molecular markers. Here we demonstrate the general utility of a technique that provides large numbers of informative loci in sharks.
Abstract: Anthropogenic impacts are believed to be the primary threats to the eastern Australian population of grey nurse sharks (Carcharias taurus), which is listed as critically endangered, and the most threatened population globally. Analyses of 235 polymorphic amplified fragment length polymorphisms (AFLP) loci and 700 base pairs of mitochondrial DNA control region provide the first account of genetic variation and geographical partitioning (east and west coasts of Australia, South Africa) in C. taurus. Assignment tests, analysis of relatedness and Fst values all indicate that the Australian populations are isolated from South Africa, with negligible migration between the east and west Australian coasts. There are significant differences in levels of genetic variation among regions. Australian C. taurus, particularly the eastern population, has significantly less AFLP variation than the other sampling localities. Further, the eastern Australian sharks possess only a single mitochondrial haplotype, also suggesting a small number of founding individuals. Therefore, historical, rather than anthropogenic processes most likely account for their depauperate genetic variation. These findings have implications for the viability of the eastern Australian population of grey nurse sharks.
Abstract: Despite the role of Australian native bees in important ecological processes, surprisingly little is known of their population structuring. In this study five microsatellite loci were used to investigate genetic structuring of the allodapine bee Exoneura robusta sampled from four locations (maximum pairwise distance c. 35 km) in the Mountain Ash forests of Victoria. Although E. robusta would seem to have high dispersal ability, several analyses show significant population subdivision and a strong pattern of isolation-by-distance from which limited gene flow was inferred. Limited gene flow was not associated with inbreeding at the within-colony level, and within-colony genetic structure implied co-founding, multiple breeding pairs and some degree of reproductive skew. Strong population structure at such fine scales suggests that substantially divergent populations are likely within the extensive distribution currently ascribed to E. robusta.
Abstract: The brushtail possum (Trichosurus vulpecula) is in decline throughout much of its natural range with the notable exception of urban areas and a few islands. In some urban areas, its density can be high enough to cause conflict with householders. We provide the first genetic-based study of dispersal for T. vulpecula in the urban environment. Seven microsatellite markers were used to investigate genetic structure of adult male (n = 53) and female ( n = 39) possums sampled from mainland suburbs of Sydney, and on nearby Scotland Island. Samples from Scotland Island also provide an opportunity to assess the effect of isolation on genetic variability, which, as theory would predict, was significantly lower than observed in mainland samples. Male-biased dispersal was inferred from patterns of relatedness between individuals of each sex. Average relatedness was significantly higher between adult female possums than between adult male possums sampled within the same garden area. In addition, males were genotypically more similar to one another at substantially greater geographic distances than females. Along with male-biased dispersal, strong localised genetic structure for both sexes infers generally high philopatry. Dispersal distances were greatest for adult male possums sampled from mainland locations. However, even for these males, genotypic similarity between possums separated by distances further than similar to 900 m was lower than the sample average, suggesting infrequent dispersal beyond this distance. Knowledge of dispersal patterns is important to managing the density levels of overabundant T. vulpecula in urban areas.
Abstract: Knowledge of processes that lead to genetic erosion for a range of species is important for conservation management. Relatively little work has assessed anthropogenic impacts on genetic variation in lizards. As part of our research program investigating effects of habitat fragmentation on Cunningham’s skink (Egernia cunninghami), allelic diversity at 10 microsatellite loci was assessed in deforested and adjacent naturally vegetated habitats at two locations on the Central tablelands of NSW, Australia. Previously we have shown that deforestation is associated with significantly reduced dispersal, but not increased levels of inbreeding and homozygosity, presumably owing to strong kin avoidance in mate choice. However, in this study, two measures of allelic diversity, allelic richness and the ratio of allele number to size range, indicate that local levels of variability are lower in deforested habitats. Levels of allelic diversity may be expected to decrease more rapidly than levels of heterozygosity, thereby flagging potential longer-term problems, such as inbreeding depression or reduced recruitment because of mate limitation through strong inbreeding avoidance.
Abstract: Habitat fragmentation/alteration has been proposed as a distinct process threatening the viability of populations of many organisms. One expression of its impact may be the disruption of core population processes such as inbreeding avoidance. Using the experimental design outlined in our companion paper, we report on the impact of habitat alteration (deforestation) on inbreeding in the rock-dwelling Australian lizard Egernia cunninghami. Ten microsatellite loci were used to calculate relatedness coefficients of potential and actual breeding pairs, and to examine mate-choice and heterozygosity. Despite significantly less dispersal and higher within-group relatedness between potential mates in deforested than in natural habitats, this did not result in significantly more inbred matings. Average relatedness amongst breeding pairs was low, with no significant difference between natural and fragmented populations in relatedness between breeding pairs, or individual heterozygosity. Active avoidance of close kin as mates was indicated by the substantially and significantly lower relatedness in actual breeding pairs than potential ones. These facts, and heterozygote excesses in all groups of immature lizards from both habitats, show that E. cunninghami maintained outbreeding in the face of increased accumulation of relatives.
Abstract: While habitat alteration has considerable potential to disrupt important within-population processes, such as mating and kin structure, via changed patterns of dispersal, this has rarely been tested. We are investigating the impact of anthropogenic habitat alteration on the population biology of the rock-dwelling Australian lizard Egernia cunninghami on the Central Tablelands of New South Wales, Australia, by comparing deforested and adjacent naturally vegetated areas. The novel analyses in this paper, and its companion, build on previous work by adding a new replicate site, more loci and more individuals. The additional microsatellite loci yield sufficient power for parentage analysis and the sociobiological inferences that flow from it. Genetic and capture-mark-recapture techniques were used to investigate mate and site fidelity and associated kin structure. Analyses of the mating system and philopatry using 10 microsatellite loci showed high levels of site fidelity by parents and their offspring in natural and deforested habitats. Parentage assignment revealed few individuals with multiple breeding partners within seasons and fidelity of pairs across two or more breeding seasons was typical. Despite reduced dispersal, increased group sizes and significant, dramatic increases in relatedness among individuals within rock outcrops in deforested areas, no significant differences between deforested and natural areas were evident in the degree of multiple mating or philopatry of breeding partners within and across seasons. With the exception that there was a significantly higher proportion of unmated males in the deforested area, the social and mating structure of this species has so far been surprisingly robust to substantial perturbation of dispersal and relatedness structure. Nonetheless, approximately 10-fold elevation of mean pairwise relatedness in the deforested areas has great potential to increase inbred matings, which is investigated in the companion paper.
Abstract: Social structuring and within-group genetics are rarely studied in lizards, but are of considerable conservation importance. In particular, the impact of anthropogenic habitat fragmentation upon fine-scale genetic patterns is largely unknown. This is being investigated for Egernia cunninghami, a species with generally low dispersal and high levels of within-group relatedness. Estimating parentage in wild populations in which close relatives may be candidate parents requires high levels of exclusionary power. The five characterized loci possess 13-29 alleles, and high polymorphic information contents (0.800-0.917) and add greatly to the markers, cloned from related skinks, currently available.
Abstract: The effects of habitat fragmentation on processes within and among populations are important for conservation management. Despite a broad spectrum of lifestyles and the conservation significance of many reptiles, very little work on fine-scale population genetics has been carried out on this group. This study examines the dispersal patterns of a rock crevice-dwelling lizard, Cunningham's skink (Egernia cunninghami), in a naturally vegetated reserve and an adjacent deforested site. Both genotypic and genic approaches were employed, using microsatellite loci. The spatial organization of individuals with respect to pairwise relatedness coefficients and allele frequencies, along with assignment tests, were used to infer dispersal characteristics for both sexes in a natural and a cleared area. The distribution of relatedness in both habitats was spatially structured, with E. cunninghami showing high pairwise relatedness within their rocky retreat sites. Analysis of relatedness over different spatial scales, spatial autocorrelation of alleles and assignment tests, all indicated that both sexes in the cleared area show less dispersal than their counterparts in the reserve. Furthermore, deforestation may inhibit female dispersal to a greater extent than that of males. The geographical structuring of allele frequencies for adults in the cleared area, but not the reserve, indicates that habitat fragmentation has the potential to alter at least the microevolution of E. cunninghami populations.
