Sleeping with the ‘enemy’: hybridization of an endangered tree weta
While hybridization is an important part of the evolutionary process, for rare species mating with more common species hybridization can increase the risks of extinction. By mating with heterospecifics rare species waste valuable reproductive resources and as a result population sizes may decline. If introgression occurs, the rare species can become genetically swamped by alleles from the more common species, rendering it effectively extinct. As a consequence of these risks, hybridization with the more common species Hemideina femorata (Canterbury tree weta) may lead to the extinction of the range restricted species H. ricta (Banks Peninsula tree weta) on Banks Peninsula. The current study uses spatial interpolation to model the distribution of each species and the potential sympatric zone to guide sampling efforts. Polymorphic microsatellite markers and mitochondrial sequence data were used to determine the extent of hybridization between H. ricta and H. femorata. The results confirm that hybridization is possible between these species. However, hybrids and introgression appear to be very rare, suggesting that reproductive isolating barriers are present but incomplete. The threat of extinction to H. ricta via hybridization with H. femorata is low but extreme loss of habitat may cause changes to population densities that could increase the risks of hybridization. Therefore, landowners should be encouraged to conserve native bush.
KeywordsHybridization Conservation genetics Hemideina ricta Hemideina femorata Species distribution modeling
We would like to thank the Department of Conservation, University of Canterbury and Lincoln University for their support. We would also like to thank Dr Tammy Steeves and Dr Michael Schwartz for their advice on this project. In addition to her advice, Dr Mary Morgan-Richards was extremely helpful in providing tissue samples analyzed in the original study (Morgan-Richards and Townsend 1995). We would like to acknowledge Tina Troup, Gail Warwick, Gemma McLaughlin, Jac van Heugten, Josh van Heugten, Hannah Burrowes, Phillip Cochrane, Cathy Mountier, Marie McDonald, Raph Nolden, Ilina Cubrinovska, Victoria Bohle and Ayla van Loenen for their field assistance. Funding for this protect was provided by the Brian Mason Scientific and Technical Trust and Invitrogen. We are grateful for the access granted by numerous landowners across Banks Peninsula. Samples were collected under the collection permit CA-17982-FAU, held by the Entomology Research Museum, Lincoln University.
RAV, RJH and MHB completed the field work required for this study, based on computer modeling performed by RAV and RJH. RAV undertook the laboratory work. Data analysis was performed by RAV and MLH. All authors contributed to the manuscript.
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