Environmental Complexity and Biodiversity: The Multi-Layered Evolutionary History of a Log-Dwelling Velvet Worm in Montane Temperate Australia

Abstract

Phylogeographic studies provide a framework for understanding the importance of intrinsic versus extrinsic factors in shaping patterns of biodiversity through identifying past and present microevolutionary processes that contributed to lineage divergence. Here we investigate population structure and diversity of the Onychophoran (velvet worm) Euperipatoides rowelli in southeastern Australian montane forests that were not subject to Pleistocene glaciations, and thus likely retained more forest cover than systems under glaciation. Over a ~100 km transect of structurally-connected forest, we found marked nuclear and mitochondrial (mt) DNA genetic structuring, with spatially-localised groups. Patterns from mtDNA and nuclear data broadly corresponded with previously defined geographic regions, consistent with repeated isolation in refuges during Pleistocene climatic cycling. Nevertheless, some E. rowelli genetic contact zones were displaced relative to hypothesized influential landscape structures, implying more recent processes overlying impacts of past environmental history. Major impacts at different timescales were seen in the phylogenetic relationships among mtDNA sequences, which matched geographic relationships and nuclear data only at recent timescales, indicating historical gene flow and/or incomplete lineage sorting. Five major E. rowelli phylogeographic groups were identified, showing substantial but incomplete reproductive isolation despite continuous habitat. Regional distinctiveness, in the face of lineages abutting within forest habitat, could indicate pre- and/or postzygotic gene flow limitation. A potentially functional phenotypic character, colour pattern variation, reflected the geographic patterns in the molecular data. Spatial-genetic patterns broadly match those in previously-studied, co-occurring low-mobility organisms, despite a variety of life histories. We suggest that for E. rowelli, the complex topography and history of the region has led to interplay among limited dispersal ability, historical responses to environmental change, local adaptation, and some resistance to free admixture at geographic secondary contact, leading to strong genetic structuring at fine spatial scale.

Strong spatial‐genetic congruence between a wood‐feeding cockroach and its bacterial endosymbiont, across a topographically complex landscape

“…Such regions are known to promote lineage differentiation, particularly in low-mobility taxa (e.g. Garrick et al, 2008;Thomas & Hedin, 2008;Walker et al, 2009;Bull et al, 2013). If population fragmentation is a recurrent process, then some lineage splitting events will be relatively young and are therefore unlikely to be faithfully tracked by gene trees of both species (Maddison, 1997;Templeton, 2002;Garrick et al, 2010).…”

Onychophora

“…Specimens of both sexes can be maintained in the laboratory for several years at 17-18 °C in plastic jars fi lled with a 2-3 cm layer of peat covered with damp paper towels to retain moisture (Baer and Mayer 2012 ). The species covers a wide geographic range and can be collected easily from decaying logs within and around national parks throughout Tallaganda (New South Wales, Australia), where it is highly abundant (Reid 1996 ;Curach and Sunnucks 1999 ;Barclay et al 2000a , b ;Sunnucks et al 2000 ;Bull et al 2013 ). In the last two decades, E. rowelli has become the most studied onychophoran species (Blaxter and Sunnucks 2011 ), Anterior is left.…”

Genetic insights into family group co-occurrence inCryptocercus punctulatus, a sub-social woodroach from the southern Appalachian Mountains

“…A pitfall trapping study by Nalepa & Grayson (2011) confirmed that large nymphs, sub-adults, and adults do occasionally move between logs. Population genetic studies have repeatedly shown that dispersal distances of wingless saproxylic invertebrates are often very short (e.g., Sunnucks et al, 2006; Garrick et al, 2007; Garrick et al, 2008; Leschen et al, 2008; Marske et al, 2009; Walker et al, 2009; Bull et al, 2013), and this is also likely to be true of C. punctulatus  (Nalepa et al, 2002). Accordingly, following colonization of an uninhabited log by a male or female woodroach, potential mates probably arrive only from logs within close proximity.…”