similar morphological, physiological, biochemical and behavioural features ; can interbreed to produce fertile offspring; reproductively isolated from other species; speciation: the production of new species.
In a survey of mtDNA sequences of five congeneric west Atlantic reef fishes (wrasses, genus Halichoeres) with similar dispersal potential, we observed phylogeographical patterns that contradict expectations of geographical isolation, and instead indicate a role for ecological speciation.

Introduction. 2009). 53 isolation in allopatric processes may act without the need for allopatry itself, i.e., without an 54 initial period of geographical separation. Topopatry, based on isolation by distance, is a new example of an 57 intermediate case. Main conclusions The distribution of individual species of Echiniscoides is limited by climate and geographical distance. Polyploidy and hybridization are two main methods of introducing sudden reproductive isolation responsible for origin of sympatric species. We will consider both theory and experimental data that support or do not support a particular speciation model. Two types of geographical isolation and the resulting …

Geographic isolation is a term that refers to a population of animals, plants, or other organisms that are separated from exchanging genetic material with other organisms of the same species. 55 Allopatry and sympatry can be viewed as extremes of a continuum of speciation modes 56 (Fitzpatrick et al. Distance does not appear to be a major factor influencing phylogeny in this genus, but ecological speciation along a temperature gradient appears to be important. Geographic Isolation. species: a group of organisms with. Species and speciation. In this review, we first discuss the roles of chromosomal variation in speciation in the light of recent genomic data and then discuss various mechanisms of speciation by means of genic mutation and selection. Sympatric speciation: When a few individuals of a species within the same geographical area are became reproductively isolated from the main population, it forms a new species is called sympatric species and its origin is called sympatric speciation. Geographic isolation can be caused by many factors and can result in a variety of results. 1. Since Darwin's study of the Galapagos Islands, archipelagos have played a central role in understanding how new species evolve from existing ones (speciation). Islands epitomize allopatric speciation, where geographic isolation causes individuals of an original species to accumulate sufficient genetic differences to prevent them breeding with each other when they are reunited. A major goal of evolutionary biology is to understand the relative roles of geography and ecology in speciation.