Evolutionary Consequences of Restricted Gene Flow in a Marine Copepod

伯顿9409066生物种群在遗传和生理上分化，实现生殖隔离，并最终经历物种形成的过程鲜为人知。以潮间带桡足类Tigriopus calforNicus为模式系统，将确定两个特定地理位置的种群的遗传分化和生殖隔离水平：(1)Point Conept周围地区(加利福尼亚州圣巴巴拉以西)和(2)下加利福尼亚州中北部海岸。前一个地区跨越了物种历史分布的地理不连续。后一地区横跨巴哈中部海岸，最近在那里发现了繁殖孤立的老虎种群。对这一地区的一系列种群的分析将跨越似乎是早期物种形成的情况。将对两个研究区域的等位酶分化水平和DNA序列差异进行比较-一个区域以生殖隔离为标志，另一个区域则不是那么明显-以了解老虎基因流动受限的后果。除了这些描述性研究外，还将开始分析细胞色素c氧化酶(CO，EC 1.9.3.1)活性在种群间杂交中的作用。由于CO由多个核和线粒体编码的亚基组成，CO活性可能对基因组间功能整合(共适应)特别敏感。对照和回交系中CO酶活性的分析将被用来测试CO活性的正常遗传模式是否被杂交群体间的胞核相互作用所干扰。这些数据将涉及与人口结构分析有关的几个基本和应用问题。(1)线粒体DNA序列变异、核DNA序列变异、等位酶变异和繁殖亲和性之间的关系是什么？(2)DNA测序和等位酶研究对检测种群结构的相对敏感性如何？(3)物种内的mtDNA单倍型是否如系统地理学研究中通常假设的那样在功能上相等，或者特定的细胞核共适应复合体是在地理上分离的群体中进化的？(4)生物地理边界在多大程度上反映在跨越边界的物种的遗传结构中？问题(1-3)在制定分析海洋和陆地系统生物多样性的方法方面很重要，而(4)与评估全球气候变化的生物影响特别相关。

Burton 9409066 The processes by which populations of organisms differentiate genetically and physiologically, achieve reproduction isolation,and ultimately undergo speciation are poorly understood. Using the intertidal copepod Tigriopus californicus as model system, levels of genetic differentialtion and reproductive isolation will be determined for populations in two geographic locations of specific interest: (1) the region around Point Conception (west of Santa Barbara, California) and (2) the north central coast of Baja California. The former region spans a geographic discontinuity in the historic distribution of the species. The latter region extends across the central coast of Baja, where a reproductively isolated population of Tigriopus has recently been found. Analysis of a series of populations in this region will span what appears to be a case of incipient speciation. Comparisons will be made of levels of allozyme differentiation and DNA sequence divergence across the two study regions- one that is marked by reproductive isolation and one that is not so marked - to gain insight into the consequence of restricted gene flow in Tigriopus. In addition to these descriptive studies, analysis of the function of cytochrome c oxidase (CO, EC 1.9.3.1) activity in interpopulation hybrids will be initiated. Because CO is composed of multiple nuclear and mitochondrially- encoded subunits, CO activity may be particularly sensitive to intergenomic functional integration (coadaptation). Analysis of CO enzymatic activity in control and back-crossed lines will be used to test whether normal patterns of inheritance of CO activity are perturbed by cytonuclear interaction in interpopulation in crosses. Several basic and applied issues concerning analysis of population structure will be addressed by the data. (1) What are the relationships among mtDNA sequence variation, nucDNA sequence variation, allozyme variation and reproductive compatibility highly subdivided populations? (2) Wh at are the relative sensitivities of DNA sequencing and allozyme studies for detecting population structure? (3) Are mtDNA haplotypes within a species functionally equivalent as is commonly assumed in phylogeographic studies, or have specific cytonuclear coadapted complexes evolved within geographically separated populations? (4) To what extent are biogeographic boundaries reflected in the genetic structure of species that span the boundaries? Issues (1-3) are important in developing methodologies for analysis of biodiversity in marine and terrestrial systems, while (4) is particularly relevant to assessing the biological impact of global climatic change.