Barrera-Moreno, O.A. (2010). Análisis de las poblaciones de los copépodos Leptodiaptomus cf. sicilis (Copepoda: Calanoida) en los lagos de la Cuenca Oriental, México. [Analysis of the populations of the copepods Leptodiaptomus cf. sicilis (Copepoda: Calanoida) in the lakes of the Oriental Basin, Mexico.]. Tesis de Maestría en Ciencias, Universidad Nacional Autónoma de México, Ciudad de México, D.F., Mexico. 66 pp. [In Spanish; English abstract].

476801

Barrera-Moreno, O.A.

2010

66 pp. [In Spanish; English abstract]

Publication

Available for editors   [request]

The copepod Leptodiaptomus sicilis has been considered as a widely distributed species in North America, occurring in freshwater and saline lakes. In Mexico it has been found inhabiting three lakes at Cuenca Oriental: two of them being deep and permanent (La Preciosa and Atexcac; TDS: 1.1 and 6.5 g L-1 , respectively), while the other is shallow and ephemeral (El Carmen; TDS: 1.4-10 g L-1 ); the three with different limnological characteristics, island distribution, but close one from each other. Despite the possible gene flow due to the passive dispersal of their resting stages, recent evidence shows that the local adaptation and/or cryptic speciation are frequent phenomena within this type of organisms. In order to analyze if geographic isolation and salinity are important factors conducting diversification among these copepods, we analyzed: (1) the interpopulation genetic divergence by sequencing fragments of the mitochondrial gene COI, (2) the morphological divergence on structures implicated in reproduction, (3) the biological fitness (patterns of both survivorship and growing) at three experimental salinities (1.1, 3.8 and 6.5 g L-1 ), and (4) the possible genetic flow (inter and intrapopulation reproductive success) among the three populations. Our results indicate that: (1) interpopulation genetic divergence was relatively low (KP2:<2%), but the populations were clearly separated among them; (2) differences were found only in size of adults, but not in the form and proportion of the compared characters; (3) the three populations had differential tolerance to salinity, those are: (a) copepods from permanent lakes had higher fitness when exposed to their original salinity; (b) the highest salinity reduces the time of molting in all populations; (c) survivorship, molting efficiency, fertilization and hatching rates of Atexcac copepods were significantly lower at low salinities; (d) contrarily, copepods from La Preciosa had the highest values in all parameters at low salinity; (e) copepods coming from the shallow lake (El Carmen) showed a higher plasticity to salinity; and (4) interpopulation mating was successful among the three population, sexual recognition of mates, interbreeding and formation of viable hybrids were observed, although some differences occurred. These results indicate that the copepods from lakes at Cuenca Oriental belong to the same biological species, having a complex process of diversification, with important ecological barriers that apparently prevent a natural genetic flow among them, even that they have the potential to maintain it; this hypothesis is reinforced by the evidence of significant adaptation to local conditions in populations inhabiting the permanent lakes. Key words: copepods, diversification processes. local adaptation

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