Hybridization between multiple fence lizard lineages in an ecotone:: locally discordant variation in mitochondrial DNA, chromosomes, and morphology
Hybridization between multiple fence lizard lineages in an ecotone:: locally discordant variation in mitochondrial DNA, chromosomes, and morphology
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DOI：
10.1111/j.1365-294x.2006.03194.x
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发表时间：
2007-03-01
影响因子：
4.9
通讯作者：
Cole, Charles J.
中科院分区：
文献类型：
--
作者：
Leache, Adam D.;Cole, Charles J.
我们调查了两个主要谱系的栅栏蜥蜴（Sceloporus cowlesi和Sceloporus tristichus）在亚利桑那州东部的Sceloporus undulatus物种复杂的混合区。这一地带位于大盆地草原和针叶林生境之间的生态交错带。我们分析了mtDNA（N = 401; 969 bp），染色体（N = 217）和形态（N = 312; 11个字符）的空间变异，以表征杂交区和评估物种的限制。一个精细的种群水平系统发育分析细化了这些物种之间的界限，并指出，四个非姐妹mtDNA分支（三个属于S。tristichus和S. cowlesi）在该地带的中心同域分布。对最接近杂交区中心的种群细胞核不平衡的估计表明，S。tristichus分支是随机交配的，而S. Cowlesi单倍型与核等位基因具有显著的非随机关联。最大似然曲线拟合分析表明，核型，形态和背色模式的倾斜都是一致的，但mtDNA的倾斜显着向南。利用20世纪70年代初和2002年收集的核型数据的渐变群中心的时间比较表明，渐变群可能已经转移了约1.5公里的北部超过30年的时间。最近向北扩张的杜松树到小科罗拉多河流域，导致激烈的牛过度放牧提供了一个合理的机制，一个移动的混合区和渗入的mtDNA单倍型，这似乎是选择性中性。很明显，复杂的相互作用在这个接触区同时进行，包括S内种群之间杂交的形成。tristichus具有诊断mtDNA，形态，核型和背色模式，以及这些与远亲但形态上隐藏的mtDNA谱系之间的次级接触（S. cowlesi）。
We investigated a hybrid zone between two major lineages of fence lizards (Sceloporus cowlesi and Sceloporus tristichus) in the Sceloporus undulatus species complex in eastern Arizona. This zone occurs in an ecotone between Great Basin Grassland and Conifer Woodland habitats. We analysed spatial variation in mtDNA (N = 401; 969 bp), chromosomes (N = 217), and morphology (N = 312; 11 characters) to characterize the hybrid zone and assess species limits. A fine-scale population level phylogenetic analysis refined the boundaries between these species and indicated that four nonsister mtDNA clades (three belonging to S. tristichus and one to S. cowlesi) are sympatric at the centre of the zone. Estimates of cytonuclear disequilibria in the population closest to the centre of the hybrid zone suggest that the S. tristichus clades are randomly mating, but that the S. cowlesi haplotype has a significant nonrandom association with nuclear alleles. Maximum-likelihood cline-fitting analyses suggest that the karyotype, morphology, and dorsal colour pattern clines are all coincident, but the mtDNA cline is skewed significantly to the south. A temporal comparison of cline centres utilizing karyotype data collected in the early 1970s and in 2002 suggests that the cline may have shifted by approximately 1.5 km to the north over a 30-year period. The recent northward expansion of juniper trees into the Little Colorado River Basin resulting from intense cattle overgrazing provides a plausible mechanism for a shifting hybrid zone and the introgression of the mtDNA haplotypes, which appear to be selectively neutral. It is clear that complex interactions are operating simultaneously in this contact zone, including the formation of hybrids between populations within S. tristichus having diagnostic mtDNA, morphology, karyotypes, and dorsal colour patterns, and secondary contact between these and a distantly related yet morphologically cryptic mtDNA lineage (S. cowlesi).