Morphological, ecological, reproductive and molecular evidence for Leptodiaptomus garciai (Osorio-Tafall 1942) as a valid endemic species

• Published in: Journal of plankton research 2008-10, Vol.30 (10), p.1079-1093
• Main Authors: Montiel-Martínez, Aideé, Ciros-Pérez, Jorge, Ortega-Mayagoitia, Elizabeth, Elías-Gutiérrez, Manuel
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Aquatic crustaceans; Biological and medical sciences; Breeding; Copepoda; Cytochromes; Diaptomus; Divergence; Ecophysiology; Endemic species; Eutrophication; Fresh water; Fundamental and applied biological sciences. Psychology; General aspects; Inland water environment; Inland waters; Lakes; Leptodiaptomus; Mitochondria; Nucleotide sequence; Nucleotides; Parapatric populations; Plankton; Reproductive isolation; Salinity tolerance; Specialization; Survival; Synecology; Temporary ponds; Tolerance
• ISSN: 0142-7873; 1464-3774
• DOI: 10.1093/plankt/fbn067

The aim of this work is to elucidate the biological and taxonomic status of a copepod from a hyposaline lake originally described as Diaptomus garciai but later synonymized with the freshwater Leptodiaptomus novamexicanus. We compared parapatric populations of L. novamexicanus s. l., from the deep Lake Alchichica (hyposaline and oligotrophic) and from temporary ponds (freshwater and hypereutrophic), using morphological analyses, molecular markers, ecophysiological tests (salinity tolerance) and inter- and intrapopulation breeding trials. Morphological analysis showed slight but consistent differences among the freshwater (specific conductivity at 25°C K25=: 440 μS cm−1) and hyposaline (K25 = 13 300 μS cm−1) populations. Fitness of copepods from Lake Alchichica was dramatically reduced at salinities lower than 4.5 g L−1 (K25 = 8100 μS cm−1). The opposite was true for the freshwater populations which were not able to survive, grow or reproduce at salinities higher than 2.5 g L−1 (K25 = 4680 μS cm−1). Interbreeding was not observed between individuals from freshwater and brackish populations. Additionally, there was an important divergence in nucleotide sequence variation (mitochondrial gene cytochrome oxidase subunit I) between L. garciai and the freshwater populations (KP2: 4.4–8.4%). Based on ecological specialization, reproductive isolation, morphological and molecular divergence, we conclude that L. garciai is a different biological species from L. novamexicanus and a valid taxon.