Fragmentation and Genetic Diversity in Romnalda (Dasypogonaceae), a Rare Rain forest Herbaceous Genus from New Guinea and Australia

Abstract

Rain forests are expected to be amongst the ecosystem types most affected by fragmentation due to their high species diversity, high endemism, complexity of interactions, and contrast with surrounding altered matrix. Due to their shorter life cycles and dependence on canopy cover, rain forest understory herbs are expected to indicate the effects of recent fragmentation more rapidly than canopy trees. This study investigated all four known species of the genus Romnalda, all of which are rare rain forest herbaceous species, to investigate the possible effects of habitat fragmentation and isolation on genetic diversity and gene flow. Allozymes were used as genetic markers and regional remnant vegetation maps were used to compare landscape fragmentation. We found that R. strobilacea populations in a highly fragmented landscape were genetically depauperate compared with those of its congeneric species that are found within continuous rain forest habitats and that allelic diversity decreased with decreasing population size but not geographic distance in R. strobilacea. Given the similarity among the species, our results indicate that all Romnalda species are potentially susceptible to loss of genetic diversity due to habitat fragmentation within relatively short timeframes. The results indicate that populations are not highly genetically differentiated and there is little evidence of genetic provenance where the species have restricted geographic ranges. Thus, species recovery programs would be better to focus on maintaining population size and genetic diversity rather than population differentiation.

Do habitat fragmentation and fire influence variation of plant species composition, structure and diversity within three regional ecosystems on the Sunshine Coast, Queensland, Australia?

“…Recent studies by Godefroid and Koedam (2003), Cagnolo et al (2006), Aparicio et al (2008), Brown and Boutin (2009), Gonzalez et al (2010) and Laurance et al (2011) have supported this relationship. Smaller, and therefore more isolated, patches are predicted to support smaller, genetically similar species populations that are vulnerable to localised extinction from disease, population decline and altered microclimatic conditions (Connor and McCoy 1979;Baldwin and Bradfield 2007;Shapcott et al 2009). …”

“…Isolation can impede the dispersal of seed and pollen both abiotically and biotically, therefore reducing emigration and immigration between communities (White et al 2004;Cramer et al 2007;Alados et al 2009). Isolated patches, irrespective of patch size are therefore still vulnerable to population decline and, therefore, localised to extinctions (Baldwin and Bradfield 2007;Shapcott et al 2009). This is important with respect to keystone species, because a significant alteration of structure and therefore microclimate can lead to altered disturbance regimes (e.g.…”

Evaluating the rarity and genetic structure of populations of the endangered Australian endemic plant Trioncinia retroflexa (Asteraceae): potential consequences for management and conservation

“…Furthermore, associations between genetic and geographic distance could be indicative of clinal variation in what was once a continuous distribution prior to habitat destruction. However, such the interpretations propose the impact of vicariance (Shepherd and Perrie 2011) and or the presence of an inhospitable landscape matrix (Shapcott et al 2009). As T. retroflexa lacks an isolating geological event, within the species' range, and continues to persist in marginal habitats (road verges and stock routes), the relevance of such explicative scenarios is up to interpretation.…”

“…Further, it is often assumed that anthropogenic environmental changes have led to retractions of rare species' distributions, from assumed large-to highly restricted and often fragmented ranges since human activities started in such species' ranges. Though this is undoubtedly sometimes the case (Bartgis, 1997;Cozzolino, et al 2003;Jacquemyn, et al 2007;Shapcott, et al 2009;Young et al 1999), there are known examples of plant species with naturally high fragmented, restricted and isolated distributions (Gilani, et al 2009;Shepherd and Perrie 2011). Because so few plant species have been well studied, it is not surprising that it is often unclear whether plant species have become rare due to human activities, or are simply persisting in their natural condition under global change.…”

“…This problem is exacerbated by a lack of information about the ecology of most rare and endangered species under previous or current conditions. This issue is even more severe for plants than vertebrates as they receive less research attention and conservation money (Escaravage, et al 2011;Schemke, et al 1994;Shapcott et al 2009;Zhao et al 2006). …”