Abstract
The Hyalella species diversity in the high-altitude water bodies of the Andean Altiplano is addressed using mitochondrial cox1 sequences and implementing different molecular species delimitation criteria. We have recorded the presence of five major genetic lineages in the Altiplano, of which one seems to be exclusive to Lake Titicaca and nearby areas, whereas the rest occur also in other regions of South America. Eleven out of 36 South American entities diagnosed by molecular delimitation criteria in our study are likely endemic to the Titicaca and neighbouring water bodies. We have detected a remarkable disagreement between morphology and genetic data in the Titicacan Hyalella, with occurrence of several cases of the same morpho-species corresponding to several Molecular Operational Taxonomic Units (MOTUs), some even distantly related, and other instances where a particular MOTU is shared by a morphologically heterogeneous array of species, including species with body smooth and others with body heavily armoured. Species diversification and incongruence between morphological and molecular boundaries within this species assemblage may be associated to the sharp changes in hydrological conditions experienced by the water bodies of the Altiplano in the past, which included dramatic fluctuations in water level and salinity of Lake Titicaca. Such environmental shifts could have triggered rapid morphological changes and ecological differentiation within the Hyalella assemblage, followed by phenotypic convergence among the diverse lineages. Factors such as phenotypic plasticity, incomplete lineage sorting or admixture between divergent lineages might lie also at the root of the morphological-genetic incongruence described herein.
Highlights
Ancient lakes – those with an uninterrupted history of more than 100,000 years (Gorthner, 1994) – are remarkable by their exceptional species richness compared to other continental water bodies
Adamowicz et al (2018) used Barcode Index Numbers (BINs), a method that implements a species threshold value of 2%, to detect 48 BINs among their South American Hyalella data set, twelve of them occurring at the Titicaca area including six uniquely sampled in the lake itself
The use of a single threshold for species delimitation can be problematic in island and islandlike rapid radiating lineages (Monaghan et al, 2006)
Summary
Ancient lakes – those with an uninterrupted history of more than 100,000 years (Gorthner, 1994) – are remarkable by their exceptional species richness compared to other continental water bodies. A remarkable aspect of these swarms of lacustrine species is the frequent occurrence of a mismatch between species delimited based on DNA sequences and those demarcated following more traditional, morphology-based criteria (Kroll et al, 2012; Naumenko et al, 2017) Such taxonomic decoupling has been recorded to occur in some of the large radiations of oceanic island terrestrial invertebrates and may be related to the fast speciation rate that concurs on such insular environments (Monaghan et al, 2006; Fryer, 1996; Cristescu et al, 2010).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
