richards-whole-thesis.pdf (4.01 MB)
An ecological, morphological and molecular investigation of Beddomeia species (Gastropoda: Hydrobiidae) in Tasmania
thesisposted on 2023-05-26, 05:09 authored by Richards, K
Narrow-range endemic species are thought to have naturally small distributions, limited by size, mobility, dispersal capabilities, specific habitat requirements and biogeographical boundaries. Many narrow range taxa are poorly reserved and most threatened freshwater invertebrate taxa in Tasmania, including the majority of Beddomeia species, fall into this category. Management of such taxa is reliant on informed ecological data which is not currently available for many freshwater invertebrates. To address the need for more detailed information on one such group of aquatic invertebrates, this study obtained spatial and ecological data for a number of Beddomeia species and identified habitat variables that together explained the snail distributions. A combination of geology, catchment size, forest type, flow and disturbance were identified as significant explanatory variables of Beddomeia presence within a river catchment. The distribution of some Beddomeia species is greater than previously predicted (at the catchment level), the Beddomeia spp. investigated were shown to occupy a wider number of streams than previously thought, suggesting that this is likely to be observed in other Beddomeia species. Detailed population structure data supported the previously held belief that Beddomeia spp. are long-lived and have low fecundity. Anthropogenic disturbance to streams, resulting from agricultural and forestry operations has previously been identified as a potential risk to aquatic invertebrates, particularly narrow-range endemics, but this has not, until now, been tested for Beddomeia species. The effects of cable-harvesting forestry disturbance on a high density Beddomeia sp. population were investigated. Population data indicated a recovery of population structure, if not abundance, within five years post-harvest, suggesting a higher level of tolerance to disturbance than had been previously anticipated. Sympatric associations between Hydrobiidae are not uncommon and were observed for Beddomeia spp. in many of the streams investigated. Several morphotypes from each of the two major study catchments, initially determined by shell measurements, were taxonomically described using a combination of external and internal characters that indicate a high level of intraspecific shell variation occurs, and failed to support the number of morphotypes identified using shell characters alone. The molecular taxonomic resolution within the genus Beddomeia was also explored, but the monophyly of the genus remains unresolved owing to the disparity of topologies recovered. Results obtained from these studies are used to review the management of Beddomeia and indicate that current measures are likely to be sufficient for headwater streams supporting the Beddomeia populations investigated, but a precautionary approach is required for other species for which there is limited information, and extra conservation measures may be necessary for those species proven to be restricted to a low number of locations.
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