Speciation in the Cladophorales species flock of ancient Lake Baikal

<p>Understanding speciation is one of the great challenges in evolutionary biology as many of the processes involved in speciation, as well as the forces leading to morphological and genetic differentiation, are not fully understood. Three main modes of speciation have been described: allopatric, parapatric and sympatric. Sympatric speciation is the most enigmatic mode because in the absence of physical barriers, disruptive selection, assortative mating and hybridization play central roles in reproductive isolation. Although it is accepted that sympatric speciation is possible, only a few examples of this process exist to date. Another common method of speciation in plants and algae is via polyploidization. Recently, a promising system to study speciation in sympatry was discovered: the endemic Cladophorales species flock in ancient Lake Baikal, Russia. The flock consists of sixteen taxa grouped in four genera: Chaetocladiella, Chaetomorpha, Cladophora and Gemmiphora. In spite of their morphological diversity, recent molecular analyses have shown that this is a monophyletic group with low genetic variation and nested within the morphologically simple genus Rhizoclonium. Due to their high number of species, endemism and sympatric distribution, many interesting questions have arisen such as what processes are involved in speciation, and whether this group might be a novel example of sympatric speciation. In this study, we analysed the population genetics of the endemic Baikalian Cladophorales to infer the processes shaping the evolution of the group. First, a set of microsatellites was designed using high-throughput sequencing data. Second, species delimitation methods based on genetic clustering were performed. Third, the population genetics of three widely distributed species was analysed looking for evidence of panmixia, a common criteria to support sympatric speciation. A total of 11 microsatellites that mostly cross-amplify between most species were obtained. The genotyping revealed that most loci had more than two alleles per individual indicating polyploidy. As such, the analyses required a different approach which consisted in coding the genotypes as ‘allelic phenotypes’, allowing the use of individuals of different ploidy levels in the same data set. The species delimitation of 15 operative morphotaxa and 727 individuals supported reproductive isolation of five morphotaxa and two hypotheses of conspecificity. However, some morphotaxa showed unclear assignments revealing the need of further research to clarify their reproductive limits. Finally, the population genetics of Chaetomorpha moniliformis, Cladophora compacta and Cl. kursanovii revealed patterns of genetic variation and structure that suggest different reproductive strategies and dispersal abilities. This demonstrates that contrasting biological characteristics may arise in closely related lineages: Chaetomorpha moniliformis with dominant asexual reproduction and long dispersal abilities; Cladophora compacta with high genetic diversity, no population structure and likely to reproduce sexually; Cl. kursanovii with a structure congruent with geographic distribution and more restricted dispersal. The results suggest that polyploidy, rather than speciation with gene flow, is the force driving the reproductive isolation and evolution of this flock. Although many questions remain to be studied, this research provides the first insights into the diversification of this Cladophorales species flock and contributes to the understanding of speciation in freshwater algae.</p>

Speciation in the Cladophorales species flock of ancient Lake Baikal

<p>Understanding speciation is one of the great challenges in evolutionary biology as many of the processes involved in speciation, as well as the forces leading to morphological and genetic differentiation, are not fully understood. Three main modes of speciation have been described: allopatric, parapatric and sympatric. Sympatric speciation is the most enigmatic mode because in the absence of physical barriers, disruptive selection, assortative mating and hybridization play central roles in reproductive isolation. Although it is accepted that sympatric speciation is possible, only a few examples of this process exist to date. Another common method of speciation in plants and algae is via polyploidization. Recently, a promising system to study speciation in sympatry was discovered: the endemic Cladophorales species flock in ancient Lake Baikal, Russia. The flock consists of sixteen taxa grouped in four genera: Chaetocladiella, Chaetomorpha, Cladophora and Gemmiphora. In spite of their morphological diversity, recent molecular analyses have shown that this is a monophyletic group with low genetic variation and nested within the morphologically simple genus Rhizoclonium. Due to their high number of species, endemism and sympatric distribution, many interesting questions have arisen such as what processes are involved in speciation, and whether this group might be a novel example of sympatric speciation. In this study, we analysed the population genetics of the endemic Baikalian Cladophorales to infer the processes shaping the evolution of the group. First, a set of microsatellites was designed using high-throughput sequencing data. Second, species delimitation methods based on genetic clustering were performed. Third, the population genetics of three widely distributed species was analysed looking for evidence of panmixia, a common criteria to support sympatric speciation. A total of 11 microsatellites that mostly cross-amplify between most species were obtained. The genotyping revealed that most loci had more than two alleles per individual indicating polyploidy. As such, the analyses required a different approach which consisted in coding the genotypes as ‘allelic phenotypes’, allowing the use of individuals of different ploidy levels in the same data set. The species delimitation of 15 operative morphotaxa and 727 individuals supported reproductive isolation of five morphotaxa and two hypotheses of conspecificity. However, some morphotaxa showed unclear assignments revealing the need of further research to clarify their reproductive limits. Finally, the population genetics of Chaetomorpha moniliformis, Cladophora compacta and Cl. kursanovii revealed patterns of genetic variation and structure that suggest different reproductive strategies and dispersal abilities. This demonstrates that contrasting biological characteristics may arise in closely related lineages: Chaetomorpha moniliformis with dominant asexual reproduction and long dispersal abilities; Cladophora compacta with high genetic diversity, no population structure and likely to reproduce sexually; Cl. kursanovii with a structure congruent with geographic distribution and more restricted dispersal. The results suggest that polyploidy, rather than speciation with gene flow, is the force driving the reproductive isolation and evolution of this flock. Although many questions remain to be studied, this research provides the first insights into the diversification of this Cladophorales species flock and contributes to the understanding of speciation in freshwater algae.</p>

Specialization on Ficus Supported by Genetic Divergence and Morphometrics in Sympatric Host-Populations of the Camellia Aphid, Aphis aurantii

Adaptation to different host plants is considered to be an important driver of the divergence and speciation of herbivorous insects. The application of molecular data and integrated taxonomic practices in recent years may contribute to our understanding of population divergence and speciation, especially for herbivorous insects considered to be polyphagous. Aphis aurantii is an important agricultural and forestry pest with a broad range of host plants. In this study, samples of A. aurantii feeding on different host plants in the same geographical area were collected, and their population genetic divergence and morphological difference were analyzed. Phylogenetic analysis and haplotype network analysis based on five genes revealed that the population on Ficus exhibited significantly genetic divergence from populations on other host plants, which was also supported by the statistical analysis based on measurements of 38 morphological characters. Our results suggest that A. aurantii has undergone specialized evolution on Ficus, and the Ficus population may represent a lineage that is experiencing ongoing sympatric speciation.

The emergence of ecotypes in a parasitoid wasp: a case of incipient sympatric speciation in Hymenoptera?

Background To understand which reproductive barriers initiate speciation is a major question in evolutionary research. Despite their high species numbers and specific biology, there are only few studies on speciation in Hymenoptera. This study aims to identify very early reproductive barriers in a local, sympatric population of Nasonia vitripennis (Walker 1836), a hymenopterous parasitoid of fly pupae. We studied ecological barriers, sexual barriers, and the reduction in F1-female offspring as a postmating barrier, as well as the population structure using microsatellites. Results We found considerable inbreeding within female strains and a population structure with either three or five subpopulation clusters defined by microsatellites. In addition, there are two ecotypes, one parasitizing fly pupae in bird nests and the other on carrion. The nest ecotype is mainly formed from one of the microsatellite clusters, the two or four remaining microsatellite clusters form the carrion ecotype. There was slight sexual isolation and a reduction in F1-female offspring between inbreeding strains from the same microsatellite clusters and the same ecotypes. Strains from different microsatellite clusters are separated by a reduction in F1-female offspring. Ecotypes are separated only by ecological barriers. Conclusions This is the first demonstration of very early reproductive barriers within a sympatric population of Hymenoptera. It demonstrates that sexual and premating barriers can precede ecological separation. This indicates the complexity of ecotype formation and highlights the general need for more studies within homogenous populations for the identification of the earliest barriers in the speciation process.

Differences in microhabitat and morphology of two sympatric congeneric species Palaquium maliliensis and Palaquium obovatum in the education forest of Hasanuddin University

Two species of Palaquium (P. maliliensis and P. obovatum) were found coexist in same habitat in the educational forest of Hasanuddin University (Unhas). Two or more species are living in a habitat could be formed from similar parent through genetic isolation process without geographic isolation and was classified as sympatric congeneric species. So far, sympatric congeneric species is still controversial among researchers. Based on this case, the purpose of this study was to determine the microhabitat and morphological differences between the two species. The methods of the study were conducted by purposively selecting 21 samples of P. maliliensis and 20 samples of P. obovatum at the tree level. In each samples found, the microhabitat characteristics (topographic position and slope) and morphological characteristics (leaf, buttress root, and morphological in general) were observed. Morphological measurement data were analyzed with correlation test for intra-species variable and real difference test for inter-species variable. This study concluded that the slope was one of the major microhabitat factors that has driven the process of sympatric speciation between P. maliliensis and P. obovatum. In morphological characteristics, differences between P. maliliensis and P. obovatum appeared in the form of leaves.

Trophic specialization on unique resources in one of the most celebrated examples of sympatric speciation, Barombi Mbo crater lake cichlids

Divergent ecological selection often results in trophic niche partitioning and is one of the central processes underlying sympatric speciation. However, there are still few studies of niche partitioning in putative examples of sympatric speciation in the wild. Here we conducted the first quantitative study of dietary niche partitioning in one of the most celebrated examples of sympatric speciation, Barombi Mbo cichlids, using stomach contents and stable isotope analyses. We found little evidence for trophic niche partitioning among any Barombi Mbo cichlids, even among the nine species coexisting in sympatry in the littoral zone. Stable isotope analyses supported these conclusions of minimal dietary overlap. However, we did find extraordinary dietary specialization in some species, including spongivory and feeding on terrestrial ants, both unique feeding strategies among freshwater fishes. Stomach contents of the spongivore (Pungu maclareni) were 20% freshwater sponge, notable considering that only 0.04% of all fishes consume sponges. Overall, we conclude that while there is less trophic niche partitioning than expected among Barombi Mbo cichlids, there is evidence for dietary specialization on rare resources in support of Liem's paradox.

The Carbon-Based Evolutionary Theory (CBET)

It is desirable to upgrade previous evolutionary theories, which have remained incomplete and controversial for decades. Here we employ the concept of carbon-based entities (CBEs), which include methane, amino acids, proteins, organisms, and other entities containing relatively many carbon atoms. We deduce the driving force, mechanisms, steps, modes, tempos of CBE evolution, through integration of biology, physics, and chemistry using logics for complex issues. We hence establish the Carbon-Based Evolutionary Theory (CBET). The CBET suggests that evolution is the increase in hierarchy, diversity, fitness of CBEs under natural selection and driven by thermodynamics due to the chemical effect of the thermodynamic features of the Earth on CBEs. It provides better explanations for life origin, macroevolution events, natural selection, sympatric speciation, and evolution tempos than previous evolutionary theories. It reveals the evolutionary basis of multiple important social notions, including diversity, collaboration, altruism, obeying rules, and proper increase in freedom. It refutes some wrong notions in thermodynamics, including negative entropy (negentropy) and that biological order is equal to thermodynamic order, which have misled many people. The CBET is supported by its deduction and application. It could be a rare bridge linking laws of thermodynamics, evolution of life, and development of human society, and could have great significance in various sciences.

On the processes of sympatric speciation in the group of «yellow» wagtails in the Middle Volga region

This article discusses the mechanisms of sympatric speciation in the group of species of «yellow» wagtails based on hybridization. Interspecific and intraspecific hybridization can be attributed to the genetic mechanisms of divergence of populations of «yellow» wagtails. The existence of hybridization between the subspecies of the white-eared yellow wagtail M. flava beema and the yellow-fronted wagtail M. lutea leads to the emergence and further accumulation in the population of individuals with a light-colored head to varying degrees, the so-called «gray-headed» individuals. Intraspecific hybridization of subspecies forms of the yellow wagtail M. flava — nominative M. f. flava and white-eared M. f. beema leads to constantly occurring genotypic splits, which support intraspecific polymorphism of populations and provide the basis for further genetic divergence of these subspecies and species. The form of "gray-headed" hybrids is characterized by maximum genetic distances (1306.67–1375.67), which may correspond to the species rank. The modern polytypic complex of M. flava (in the narrow sense, a series of species and subspecies of only M. flava) probably formed in historical time on the basis of fan hybridization between the original forms of M. f. flava and M. lutea. Thus, the factors of genetic differentiation and divergence, along with ecological and geographical isolation, play a leading role in the formation of the spatio-temporal and genetic structure of the genus Motacilla. Currently, there is an active process of genetic divergence and separation of subspecies and species forms of «yellow» wagtails under conditions of wide sympatry within a single polytypic complex based on intraspecific and interspecific hybridization in the European part of Russia.

A Comprehensive Evolutionary Theory Deduced from Thermodynamics

The current evolutionary theories have remained incomplete, controversial, and stagnant for multiple decades. To solve this issue, we create the concept of carbon-based entities (CBEs) which include methane, amino acids, proteins, organisms, and other entities containing carbon atoms. We deduce from thermodynamics the driving force, the progressive mechanisms, and the major steps of evolution of CBEs, and hence establish a comprehensive evolutionary theory termed the CBE evolutionary theory (CBEET). The CBEET demonstrates that evolution is driven hierarchy-wise by thermodynamics and favors fitness and diversity. It provides novel explanations for origin of life (abiogenesis), macroevolution, natural selection, sympatric speciation, evolution tempos, animal group evolution, and human society development in a comprehensive and comprehensible way. It elucidates that collaboration, altruism, obeying rules with properly increased freedom are important throughout evolution of CBEs. It refutes thoroughly the wrong notion that negative entropy (negentropy) leads to biological order which is distinct from thermodynamic order. It integrates with research advances in multiple disciplines and bridges laws of physics, evolution in biology, and harmonious development of human society.

A Comprehensive Evolutionary Theory Deduced from Thermodynamics

Studies on evolution have made significant progress in multiple disciplines, but evolutionary theories remain incomplete, controversial and inadequate in explaining origin of life and macroevolution. Here we create the concept of carbon-based entities (CBEs) which include methane, amino acids, proteins, bacteria, animals, plants, and other entities containing carbon atoms. From thermodynamics, we deduce the driving force, the progressive mechanisms, and the major steps of CBE evolution, and hence establish a comprehensive evolutionary theory termed the CBE evolutionary theory (CBEET). CBEET highlights that evolution is driven hierarchy-wise by thermodynamics and favors fitness and diversity. It provides novel explanations for origin of life (abiogenesis), macroevolution, natural selection, sympatric speciation, and animal group evolution in a comprehensive and comprehensible way. It elucidates that collaboration, altruism, obeying rules with properly increased freedom are important throughout the CBE evolution. It refutes thoroughly the notion that negative entropy (negentropy) leads to biological order which is distinct from thermodynamic order. It integrates with research advances in multiple disciplines and bridges laws of physics, evolution in biology, and harmonious development of human society.