National Science Review: Reveal patterns of congenous speciation

Speciation is one of
the core issues in evolutionary biology research.
Sympatric speciation refers to the process by
which new species evolve from ancestral species in the same region and produce reproductive isolation without geographical isolation.
However, in the early stages of congenous speciation, frequent gene flow between species can delay or even reverse population differentiation, so this speciation model has been controversial
.

Although congenous species differentiation is theoretically possible, there are few
empirical cases.
Gymnocypris eckloni scoliostomus and piebald naked carp (G.
Eckloni eckloni is two sister species distributed in Sunmutso Lake on the Qinghai-Tibet Plateau, with differences in morphology, diet, reproduction and other characteristics, and a short differentiation time (about 20,000-60,000 years ago), which is an ideal model for studying the formation of congenous species, and is of great significance
to the theoretical study of congenous speciation.

Based on genomic data, He Shunping's team, a researcher at the Institute of Hydrobiology, Chinese Academy of Sciences, analyzed the genetic diversity, phylogeny and genetic structure, population dynamic history, gene flow, genomic island, and selection intensity of the two naked carps, supplemented by theoretical simulations, and proposed a conspecificity or micro-parapatric speciation model
.

The study proposes that the geographical scale of speciation should be defined based on gene flow in the process of speciation, for example, there is no gene flow in exotic speciation, and gene flow should be unimpeded
in isogenetic speciation.
The study found that there were 54 large genome islands (≥ 100 kb) between species, and their total length accounted for about 89.
4%
of the total length of all genome islands.
The presence of large genomic islands (≥ 100 kb) suggests that gene flow is greatly restricted
during speciation.
This is significantly different from the absence of gene flow patterns in micro-exotic speciation, but the presence of large genome islands does not support congenous speciation patterns
.
Theory and recent empirical studies suggest that sustained gene flow should produce many genomic islands
as small as a few kilobytes.
This pattern is consistent with the broad evidence for neighborhood speciation, which favors divergent selection while also allowing gene flow, albeit on a smaller
scale of microneighborhood speciation.
In addition, the genomic island contains some genes related to olfactory signaling, which may play an important role
in food selection and mating in fish.

Related research results are Sympatric or micro-allopatric speciation in a glacial lake? Genomic islands support neither, published online in
the National Science Review.
The relevant research work has been supported
by the Major Research Program of the National Natural Science Foundation of China, the Strategic Leading Science and Technology Special Project of the Chinese Academy of Sciences, and the General Fund of the National Natural Science Foundation of China.

Figure 1.
(A-C) Gene flow patterns of homonymous, heterogeneous and neighborhood speciation; (D) Schematic diagram of two species of naked carp