Phylogeoraphy of geotrochus and trochomorpha (gastropoda : trochomorp hidae) in Sabah

• Main Author: Chang, Zi Yuan
• Format: Thesis
• Language: English; English
• Published: 2020
• Subjects: QL360-599.82 Invertebrates
• Online Access: https://eprints.ums.edu.my/id/eprint/42606/1/24%20PAGES.pdf; https://eprints.ums.edu.my/id/eprint/42606/2/FULLTEXT.pdf; https://eprints.ums.edu.my/id/eprint/42606/

Sabah is renowned for species richness and endemism, and this pattern is largely due to current ecological conditions and historical events. Phylogeography studies in Sabah have been focusing on plant taxa and several animal taxa with high mobility. There is a lack of the biogeographical knowledge of species with low mobility. Therefore, Geotrochus and Trochomorpha were selected to test the biogeography hypothesis in Sabah. The taxonomy status of the two genera has been based on morphology. As shell characters are strongly influenced by ecological factors, the evolutionary relationship of the two genera is currently not truly represented. Hence, this study presents the molecular phylogeny of six Geotrochus species and three Trochomorpha species based on mitochondrial genes (COI and 16S) and nuclear gene (ITS-1). Influences of temperature, elevation and precipitation on teleoconch sculpture pattern and four quantitative shell traits were statistically examined to elucidate the reliability of the diagnostic characters. Finally, biogeography patterns of Geotrochus and Trochomorpha in Sabah were predicted using MaxEnt. Determinants of the pattern were analysed using BEAST (Bayesian evolutionary analysis by sampling trees) and the MaxEnt built-in Jackknife test. Consensus trees of ML and BI revealed the polyphyly of Trochomorpha and indicated that the teleoconch sculpture is a homoplasy character. Shell width and aperture width are both negatively correlated with elevation (SW: r= -0.42; AW: r= -0.43) and precipitation (SW: r= -0.42; AW: r= -0.43) while being positively correlated with temperature (SW: r= 0.49; AW: r= 0.49). Shell height is only positively associated with temperature (r= 0.29) while aperture height is not correlated to any of the ecological variables. The biogeography patterns of the species appear to be highly influenced by the climate in Sa bah, with the distribution of the highland species shaped by temperature, whereas lowland species appears affected by precipitation. Geotrochus and Trochomorpha diverged around Miocene to Pliocene, subsequent to the uplifting of the mountainous area and episode of sea lowering around Sabah. Furthermore, my analyses suggest that global warming will likely cause the extinction of mountaintop species such as T. rhysa and T. haptoderma while reducing the suitable habitat of G. oedobasis and T. the/ecoryphe on Mt. Kinabalu. Based on my results, the taxonomy of Geotrochus and Trochmorpha still requires further revision and future studies should include more taxa and broader geographical scale.