Fitness Implications of the Mating System and Reproductive Ecology of Tuatara

<p>Sexual selection and reproductive strategies affect individual fitness and population genetic diversity. Long-standing paradigms in sexual selection and mating system theory have been overturned with the recent integration of behavioural and genetic techniques. Much of this theory is based on avian systems, where a distinction has now been made between social and genetic partners. Reptiles provide contrast to well-understood avian systems because they are ectothermic, and phylogenetic comparisons are not hindered by complicated patterns of parental care. I investigate the implications of the mating system and reproductive ecology on individual fitness and population genetic diversity of tuatara, the sole extant representative of the archaic reptilian order Sphenodontia. Long-term data on individual size of Stephens Island tuatara revealed a density-dependent decline in body condition driven by an apparently high population growth rate resulting from past habitat modification. Spatial, behavioural, and genetic data from Stephens Island tuatara were analysed to assess territory structure, the mating system, and variation in male fitness. Large male body size was the primary predictor of 1) physical access to females, 2) competitive ability, and 3) mating and paternity success. Seasonal monogamy predominates, with probable long-term polygyny and polyandry. Annually, male reproduction is highly skewed in the wild and in captivity. Over 80% of offspring from a captive population on Little Barrier Island were sired by one male and multiple paternity was found in approximately 18% of these clutches, although it was not detected in any wild clutch. The dominance structure has lead to reduced genetic variation in the recovering Little Barrier Island population. Stephens Island tuatara show fine-scale population genetic structuring that appears to be driven by past habitat modification and a sedentary lifestyle in the absence of sex-biased dispersal or migration. These results will improve conservation management of tuatara by providing guidelines for maximising genetic diversity of small and captive populations and will aid in selecting founders for translocated populations. Because of the archaic phylogenetic position of tuatara, this study provides a baseline for comparisons of mating system evolution in reptiles.</p>

Fitness Implications of the Mating System and Reproductive Ecology of Tuatara

<p>Sexual selection and reproductive strategies affect individual fitness and population genetic diversity. Long-standing paradigms in sexual selection and mating system theory have been overturned with the recent integration of behavioural and genetic techniques. Much of this theory is based on avian systems, where a distinction has now been made between social and genetic partners. Reptiles provide contrast to well-understood avian systems because they are ectothermic, and phylogenetic comparisons are not hindered by complicated patterns of parental care. I investigate the implications of the mating system and reproductive ecology on individual fitness and population genetic diversity of tuatara, the sole extant representative of the archaic reptilian order Sphenodontia. Long-term data on individual size of Stephens Island tuatara revealed a density-dependent decline in body condition driven by an apparently high population growth rate resulting from past habitat modification. Spatial, behavioural, and genetic data from Stephens Island tuatara were analysed to assess territory structure, the mating system, and variation in male fitness. Large male body size was the primary predictor of 1) physical access to females, 2) competitive ability, and 3) mating and paternity success. Seasonal monogamy predominates, with probable long-term polygyny and polyandry. Annually, male reproduction is highly skewed in the wild and in captivity. Over 80% of offspring from a captive population on Little Barrier Island were sired by one male and multiple paternity was found in approximately 18% of these clutches, although it was not detected in any wild clutch. The dominance structure has lead to reduced genetic variation in the recovering Little Barrier Island population. Stephens Island tuatara show fine-scale population genetic structuring that appears to be driven by past habitat modification and a sedentary lifestyle in the absence of sex-biased dispersal or migration. These results will improve conservation management of tuatara by providing guidelines for maximising genetic diversity of small and captive populations and will aid in selecting founders for translocated populations. Because of the archaic phylogenetic position of tuatara, this study provides a baseline for comparisons of mating system evolution in reptiles.</p>

A Meta-Analytical Investigation of the Gap between Measured and Predicted Inter-Population Genetic Diversity in Species of High Conservation Concern—The Case of the Critically Endangered European Mink Mustela lutreola L., 1761

Although properly designed sampling in population genetic studies is of key importance for planning evidence-informed conservation measures, sampling strategies are rarely discussed. This is the case for the European mink Mustela lutreola, a critically endangered species. In order to address this problem, a meta-analysis aiming to examine the completeness of mtDNA haplotype sampling in recent studies of M. lutreola inter-population genetic diversity was conducted. The analysis was performed using the sample-size-based rarefaction and extrapolation sampling curve method for three populations—the Northeastern (Russia, Belarus and Estonia), the Western (France and Spain), and the Southeastern (Romania). The extrapolated values of the Shannon–Wiener index were determined, assuming full sample coverage. The gap between the measured and predicted inter-population genetic diversity was estimated, indicating that the identified level of sample coverage was the lowest for the NE population (87%), followed by the SE population (96%) and the W population (99%). A guide for sampling design and accounting for sampling uncertainty in future population genetic studies on European mink is provided. The relatively low sample coverage for the Russian population clearly indicates an urgent need to take conservation measures for European mink in this country.

Non-linear genetic diversity and notable population differentiation caused by low gene flow of bermudagrass [Cynodon dactylon (L.) Pers.] along longitude gradients

Background Environmental variation related to ecological habitat is the main driver of plant adaptive divergence. Longitude plays an important role in the formation of plant population structure, indicating that environmental differentiation can significantly shape population structure. Methods Genetic diversity and population genetic structure were estimated using 105 expressed sequence tag-derived simple sequence repeat (EST-SSR) loci. A total of 249 C. dactylon (L.) Pers. (common bermudagrass) individuals were sampled from 13 geographic sites along the longitude (105°57′34″–119°27′06″E). Results There was no obvious linear trend of intra-population genetic diversity along longitude and the intra-population genetic diversity was not related to climate in this study. Low gene flow (Nm = 0.7701) meant a rich genetic differentiation among populations of C. dactylon along longitude gradients. Significantly positive Mantel correlation (r = 0.438, P = 0.001) was found between genetic distance and geographical interval while no significant partial Mantel correlation after controlling the effect of mean annual precipitation, which indicated geographic distance correlated with mean annual precipitation affect genetic distance. The genetic diversity of C. dactylon with higher ploidy level was higher than that with lower ploidy level and groups of individuals with higher ploidy level were separated further away by genetic distance from the lower ploidy levels. Understanding the different genetic bases of local adaptation comparatively between latitude and longitude is one of the core findings in the adaptive evolution of plants.

The role of genetic diversity and arbuscular mycorrhizal fungal diversity in population recovery of the semi-natural grassland plant species Succisa pratensis

Ecosystem restoration is as a critical tool to counteract the decline of biodiversity and recover vital ecosystem services. Restoration efforts, however, often fall short of meeting their goals. Although functionally important levels of biodiversity can significantly contribute to the outcome of ecosystem restoration, they are often overlooked. One such important facet of biodiversity is within-species genetic diversity, which is fundamental to population fitness and adaptation to environmental change. Also the diversity of arbuscular mycorrhizal fungi (AMF), obligate root symbionts that regulate nutrient and carbon cycles, potentially plays a vital role in mediating ecosystem restoration outcome. In this study, we investigated the relative contribution of intraspecific population genetic diversity, AMF diversity, and their interaction, to population recovery of Succisa pratensis, a key species of nutrient poor semi natural grasslands. We genotyped 180 individuals from 12 populations of S. pratensis and characterized AMF composition in their roots, using microsatellite markers and next generation amplicon sequencing, respectively. We also investigated whether the genetic makeup of the host plant species can structure the composition of root-inhabiting AMF communities. Our analysis revealed that population allelic richness was strongly positively correlated to relative population growth, whereas AMF richness and its interaction with population genetic diversity did not significantly contribute. The variation partitioning analysis showed that, after accounting for soil and spatial variables, the plant genetic makeup explained a small but significant part of the unique variation in AMF communities. Our results confirm that population genetic diversity can contribute to population recovery, highlighting the importance of within-species genetic diversity for the success of restoration. We could not find evidence, however, that population recovery benefits from the presence of more diverse AMF communities. Our analysis also showed that the genetic makeup of the host plant structured root-inhabiting AMF communities, suggesting that the plant genetic makeup may be linked to genes that control symbiosis development.

Genetic variation and population structure of clonal Zingiber zerumbet at a fine geographic scale: a comparison with two closely related selfing and outcrossing Zingiber species

Background There has always been controversy over whether clonal plants have lower genetic diversity than plants that reproduce sexually. These conflicts could be attributed to the fact that few studies have taken into account the mating system of sexually reproducing plants and their phylogenetic distance. Moreover, most clonal plants in these previous studies regularly produce sexual progeny. Here, we describe a study examining the levels of genetic diversity and differentiation within and between local populations of fully clonal Zingiber zerumbet at a microgeographical scale and compare the results with data for the closely related selfing Z. corallinum and outcrossing Z. nudicarpum. Such studies could disentangle the phylogenetic and sexually reproducing effect on genetic variation of clonal plants, and thus contribute to an improved understanding in the clonally reproducing effects on genetic diversity and population structure. Results The results revealed that the level of local population genetic diversity of clonal Z. zerumbet was comparable to that of outcrossing Z. nudicarpum and significantly higher than that of selfing Z. corallinum. However, the level of microgeographic genetic diversity of clonal Z. zerumbet is comparable to that of selfing Z. corallinum and even slightly higher than that of outcrossing Z. nudicarpum. The genetic differentiation among local populations of clonal Z. zerumbet was significantly lower than that of selfing Z. corallinum, but higher than that of outcrossing Z. nudicarpum. A stronger spatial genetic structure appeared within local populations of Z. zerumbet compared with selfing Z. corallinum and outcrossing Z. nudicarpum. Conclusions Our study shows that fully clonal plants are able not only to maintain a high level of within-population genetic diversity like outcrossing plants, but can also maintain a high level of microgeographic genetic diversity like selfing plant species, probably due to the accumulation of somatic mutations and absence of a capacity for sexual reproduction. We suggest that conservation strategies for the genetic diversity of clonal and selfing plant species should be focused on the protection of all habitat types, especially fragments within ecosystems, while maintenance of large populations is a key to enhance the genetic diversity of outcrossing species.

Impact of different numbers of microsatellite markers on population genetic results using SLAF-seq data for Rhododendron species

Microsatellites (simple sequence repeats, SSRs) are co-dominant nuclear markers that are widely used in population genetic studies. Population genetic parameters from different studies might be significantly influenced by differences in marker number. In our study, 265 sequences with polymorphic microsatellites were obtained from SLAF-seq data. Then, subpopulations containing different numbers (5, 6, 7,…, 15, 20, 25, 30, 35, 40) of markers were genotyped 10 times to investigate the impact of marker numbers on population genetic diversity results. Our results show that genotyping with less than 11 or 12 microsatellite markers lead to significant deviations in the population genetic diversity or genetic structure results. In order to provide markers for population genetic and conservation studies for Rhododendron, 26 SSR primers were designed and validated in three species.