Fri 17 Nov 2017: 3.00pm [QE] – Zeng Yiwen on “Natural and human-mediated interactions between freshwater crabs and crayfish”

PhD Defense Seminar cum Oral Examination

“Natural and human-mediated interactions between freshwater crabs and crayfish”

Speaker:   Zeng Yiwen (Graduate Student Dept.of Biological Sciences, NUS)
Date:         17 Nov 2017, Friday
Time:         3pm
Venue:       Seminar Room 1 (S2 Level 4, #04-14)
Supervisor: Asst Prof Darren Yeo Chong Jinn

Abstract –  “Present day natural distributions of primary freshwater crabs and crayfish are largely allopatric, with crayfish being generally restricted to subtropical to temperate habitats globally, and crabs distributed around most tropical and sub-tropical regions. These non-overlapping distributions have been attributed to the two taxa being functionally similar, thereby having a high likelihood of interacting and competing with each other. Inter-taxa interactions can be an important biogeographical barrier to natural species dispersal. Such barriers, however, are breaking down as a result of the increased anthropogenic translocation and introduction of crayfish species beyond their native ranges into habitats containing native freshwater crabs. In spite of the implications associated with natural and human-mediated interactions between freshwater crabs and crayfish, few empirical studies have investigated such inter-taxa interactions to date, and the patterns and processes involved remain poorly understood.

I address this gap in knowledge and understanding via a series of studies at varying scales—ranging from global to regional to local. These studies involve the modeling of taxa richness and species distribution patterns (both spatially and temporally), in-situ field studies, and ex-situ behavioral experiments. Through such efforts, natural inter-taxa interaction is identified as a biotic factor that can influence biogeographical patterns of primary freshwater crabs and crayfish in some areas (e.g., the Mediterranean region), but not in others. The widespread introduction of non-indigenous crayfish species increases the chances for (human-mediated) inter-taxa interaction and competition to occur. The crayfish species Cherax quadricarinatus, for example, is predicted to co-occur and impact the greatest number of freshwater crab species in Southeast Asia regardless of future climate scenarios. This crayfish species already appears to have a negative impact on populations of the native freshwater crab, Parathelphusa maculata, within Singapore’s forest streams, with predation as well as competition for shelter being likely mechanisms for such impacts. These findings inform our understanding of the role that biotic factors can play in biogeographical processes, as well as the development and implementation of conservation strategies for native freshwater crabs.”

All are welcome