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Morphological Clines (morphological + cline)
Selected AbstractsMorphological clines in dendritic landscapesFRESHWATER BIOLOGY, Issue 9 2007A. CHAPUT-BARDY Summary 1. In complex landscapes such as river networks, organisms usually face spatio-temporal heterogeneity and gradients in geomorphological, water, ecological or landscape characteristics are often observed at the catchment scale. These environmental variables determine developmental conditions for larval stages of freshwater insects and influence adult phenotypic characteristics. Environmental clines are therefore expected to generate morphological clines. Such a process has the potential to drive gradual geographical change in morphology-dependent life history traits, such as dispersal. 2. We studied the influence of aquatic and terrestrial environmental factors on morphological variations in Calopteryx splendens across the Loire drainage. To investigate these effects we took explicitly into account the hierarchical structure of the river network. 3. We analysed eight morphological traits. Results showed significant body size variation between tributaries and the presence of a morphological cline at the drainage scale. We observed an effect of pH and water temperature on body size. Individuals in downstream sites were larger than individuals in upstream sites, and adults whose larval stages were exposed to alkaline pH and high temperatures during summer were larger. 4. Body size affects flight abilities in insects. Thus, our results suggest that morphological clines may generate an asymmetric dispersal pattern along the downstream,upstream axis, downstream populations dispersing farther than upstream ones. Such a process is expected to influence population genetic structure at the drainage scale if larval drift and floods do not balance an asymmetrical dispersal pattern of adults along the downstream,upstream gradient. To assess the influence of environmental gradients on the variation of life history traits it is important to understand the population biology of freshwater insects, and more generally of riverine organisms. It is also essential to integrate such data in conservation or restoration programmes. [source] Divergent character clines across a recent secondary contact zone in a Hispaniolan lizardJOURNAL OF ZOOLOGY, Issue 3 2008M. E. Gifford Abstract Studies of genetic contact zones provide valuable information regarding the processes of population divergence, adaptation and speciation. In this paper, I examine transitions in morphology, mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) haplotypes across a recent secondary contact zone in a Hispaniolan lizard Ameiva chrysolaema. Maximum likelihood cline fitting analyses suggest non-coincidence of cline centers and that the mtDNA cline is significantly displaced to the west of the remaining clines. nDNA and morphological clines are coincident and tend to be associated with the prevailing environmental gradient. The lack of cytonuclear disequilibrium near the center of the contact zone and the non-coincidence of character clines suggest that this zone does not conform to a tension zone model of hybridization; thus, gene flow across the zone does not seem to be impeded. The extremely narrow width of the dorsal scale size cline and the close association of this cline with the steepness of the environmental (precipitation) gradient suggest that this character may be under environmental selection. Taken together, this contact zone appears to be structured by a combination of mtDNA introgression, possibly associated with eastward movement of the zone, and environmental selection on some characters. [source] | ||||||||||