Genetic diversity of endangered orchid Phaius australis across a fragmented Australian landscape

Exploring island syndromes: Variable matrix permeability in Phalaenopsis pulcherrima (Orchidaceae), a specialist lithophyte of tropical Asian inselbergs

INTRODUCTION

Plants confined to island-like habitats are hypothesised to possess a suite of functional traits that promote on-spot persistence and recruitment, but this may come at the cost of broad-based colonising potential. Ecological functions that define this island syndrome are expected to generate a characteristic genetic signature. Here we examine genetic structuring in the orchid Phalaenopsis pulcherrima, a specialist lithophyte of tropical Asian inselbergs, both at the scale of individual outcrops and across much of its range in Indochina and on Hainan Island, to infer patterns of gene flow in the context of an exploration of island syndrome traits.

METHODS

We sampled 323 individuals occurring in 20 populations on 15 widely scattered inselbergs, and quantified genetic diversity, isolation-by-distance and genetic structuring using 14 microsatellite markers. To incorporate a temporal dimension, we inferred historical demography and estimated direction of gene flow using Bayesian approaches.

RESULTS

We uncovered high genotypic diversity, high heterozygosity and low rates of inbreeding, as well as strong evidence for the occurrence of two genetic clusters, one comprising the populations of Hainan Island and the other those of mainland Indochina. Connectivity was greater within, rather than between the two clusters, with the former unequivocally supported as ancestral.

DISCUSSION

Despite a strong capacity for on-spot persistence conferred by clonality, incomplete self-sterility and an ability to utilize multiple magnet species for pollination, our data reveal that P. pulcherrima also possesses traits that promote landscape-scale gene flow, including deceptive pollination and wind-borne seed dispersal, generating an ecological profile that neither fully conforms to, nor fully contradicts, a putative island syndrome. A terrestrial matrix is shown to be significantly more permeable than open water, with the direction of historic gene flow indicating that island populations can serve as refugia for postglacial colonisation of continental landmasses by effective dispersers.

One Step Away From Extinction: A Population Genomic Analysis of A Narrow Endemic, Tropical Plant Species

Intraspecific genetic variation plays a fundamental role in maintaining the evolutionary potential of wild populations. Hence, the assessment of genetic diversity patterns becomes essential to guide biodiversity conservation policies, particularly for threatened species. To inform management strategies for conservation of Mimosa catharinensis - a narrow endemic, critically endangered plant species - we identified 1,497 unlinked SNP markers derived from a reduced representation sequencing method (i.e., double digest restriction site associated DNA sequencing, or ddRADseq). This set of molecular markers was employed to assess intrapopulation genetic parameters and the demographic history of one extremely small population of M. catharinensis (N=33) located in the Brazilian Atlantic Forest. Contrary to what is expected for narrow endemic and threatened species with small population sizes, we observed a moderate level of genetic diversity for M. catharinensis [uH E(0%missing data)=0.205, 95% CI (0.160, 0.250); uH E(30%missing data)=0.233, 95% CI (0.174, 0.292)]. Interestingly, M. catharinensis, which is a lianescent shrub with no indication of seed production for at least two decades, presented high levels of outcrossing [t (0%missing data)=0.883, SE±0.0483; t (30%missing data)=0.909, SE±0.011] and an apparent absence of inbreeding [F (0%missing data)=-0.145, 95% CI (-0.189, -0.101); F (30%missing data)=-0.105, 95% CI (-0.199, -0.011)]. However, the reconstruction of demographic history of M. catharinensis indicated that the population should be suffered a recent bottleneck. Our population genomic study tackles a central issue in evolution and conservation biology and we expect that it will be useful to help safeguard the remaining genetic diversity reported for this unique genetic resource.

The genetic diversity and differentiation of mussels with complex life cycles and relations to host fish migratory traits and densities

Many landscape and biotic processes shape the genetic structure of populations. The genetic structure of species with parasitic stages may also depend on the life history and ecology of their host. We investigated population genetic structure of the mussel Margaritifera margaritifera in Southern Sweden, and in relation to the population size and life history of its hosts, Salmo trutta and S. salar. Mussel populations were genetically differentiated into two clusters, further subdivided into four clusters and distinct conservation units. Regardless of host species, the genetic differentiation was lower among mussel populations sustained by sea-migrating than by resident hosts, while the genetic diversity was higher in mussel populations sustained by sea-migrating than by resident hosts. Genetic diversity of mussel populations was positively related to host abundance. Mussel population size was positively related to high genetic diversity of mussels sustained by resident hosts, while low mussel population size sustained by sea-migrating hosts had a high genetic diversity. The results of our study suggest a combined influence of mussels and host fish on genetic structure of unionoid mussels. We suggest to conserve not only mussel population sizes and host fish species, but also consider host migratory/resident behaviour and abundance when designing conservation programs.

Orchid conservation and research: An analysis of gaps and priorities for globally Red Listed species

Orchids are among the most threatened taxa globally due to increasing anthropogenic threats, inherent rarity and specific conservation needs. But what are the global research and conservation priorities for this charismatic group of plants? Using information for 595 orchids on the IUCN Red List, we reviewed past research and identified key research and conservation priorities. These included understanding threats, monitoring orchid populations and habitats, species management in ex situ conservation, genome resource banks and artificial propagation, land and habitat protection and education and awareness through communication. Based on the available data, we recommend future orchid conservation and research should focus on the current gaps in knowledge and practice including monitoring population trends and distributions, ecology, threats, protection and management of species and their habitats and increasing education and awareness.