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Resolving a taxonomic ambiguity: variation in the pycnogonid Pseudopallene ambigua (Stock 1956)


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Stevenson, D (2003) Resolving a taxonomic ambiguity: variation in the pycnogonid Pseudopallene ambigua (Stock 1956). Honours thesis, University of Tasmania.

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A combination of molecular and morphological techniques was applied to resolve a
nearly 50-year-old ambiguity in the Australian pycnogonid Pseudopallene ambigua
(Stock 1956). Stock was hesitant to initially describe P. ambigua due to confusion
with a sister species P. pachychiera. More recent work has clarified the distinction
between these taxa but P. ambigua remains enigmatic with the type series suspected
to contain several species.
For this study, P. ambigua were collected from a 10-11 kilometre section of the
Tasmanian east coast around Eaglehawk Neck, SE Tasmania. The 56 specimens of P.
ambigua were examined and the data used to generate morphological groups within
this species. Samples from these morphological groups were then sequenced at two
rapidly evolving gene regions, the mitochondrial 16S ribosomal gene and the
mitochondrial cytochrome c oxidase I protein coding gene.
Comparison of the sequence data for both 16S and cytochrome c oxidase determined
that two species were present in this collection. These genetically identified species
were consistent with the morphological data. Morphological characters including
proboscis shape, oviger spine number, tibiae surface texture, heel spine pattern and
propodus width-height ratio were found to confirm the molecular 16S and COl
sequences separating a consistent group of specimens. Examination of the
morphological data provided significant evidence for the characters proboscis shape
and propodus ratio that will enable the new species to be readily identified from P.

Item Type: Thesis (Honours)
Date Deposited: 05 Dec 2011 04:28
Last Modified: 11 Mar 2016 05:54
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