Allopatric and Sympatric Speciation - Paper Example

Introduction

Savolainen et al. (2006) believe that the origin of species diversity has greatly challenged biologists for more than two centuries. Allopatric speciation is considered the divergence of species due to geographical isolation and is believed to be properly documented. Sympatric speciation, on the other hand, is considered to be a divergence without geographical isolation. Unlike allopatric speciation, sympatric speciation is not well documented but instead highly controversial. It is through the process of speciation that new species arise. During this process of speciation, an ancestral species would split into several descendant species. Genetically, these descendant species are not similar to each other and may no longer interbreed. For speciation to happen, there have to be two new populations from the original population. The new population should also evolve in a manner that it would become difficult for individuals from this newly formed populations to interbreed.

Is your time best spent reading someone else’s essay? Get a 100% original essay FROM A CERTIFIED WRITER!

Order now

Sympatric Speciation

Although sympatric speciation is controversial, various mathematical models have proven that this particular speciation can be possible. There are, however, very few documented examples. Sympatrically, the Cichlid fish is believed to have radiated in African Crater lakes. Analyses of the molecular phylogenetic prove that this species of fish in every lake has a common ancestor. This fish species' speciation is possibly driven by ecology and sexual selection (Savolainen et al., 2006). Secondly, through sympatry, races of hawthorn maggot and apple have shifted to different hosts and differ in breeding times and reproductive behavior. The African indigobirds are believed to have sympatrically speciated after colonization of new hosts.

According to Kang et al. (2017), one of the most debated topics in biology has been the probability of speciation with gene flow. Scientists have found it quite challenging to distinguish the effects of time and the effect of gene flow. In evolution, gene flow is regarded as a constraining force. There has been a growing number of examples being reported of speciation with gene flow in the recent past. These reports have advanced biologists' understanding of speciation when in the absence of a geographic obstacle. Several conceptual frameworks developed for easy and effective comparison of speciation with gene flow and speciation without gene flow. In the speciation with gene flow, the effective migration experienced across the genome depended on many factors like the number of selected loci, recombination rate, and the strength of selection. The genome's dynamic changes show that the entire genomic analysis can offer a better empirical understanding of speciation and genetic differentiation.

Adaptive Radiation

A good example of adaptive radiation is the Hawaiian Drosophila. The Hawaiian Drosophila is an endemic group found in Hawaii and are quite species-rich. The Drosophila heteroneura and the Drosophila silvestris are closely related Drosophila species believed to have occurred sympatrically. These two species are known to hybridize while they also have morphological and behavioral characteristics, which are driven mostly through sexual selection (Kang et al., 2017). The Drosophila Planitibia is the closest allopatric species related to D. heteroneura and D. silvestris. When either D. heteroneura or D. silvestris cross D. Planitibia, it exhibits male sterility.

Bradbury et al. (2010) identify adaptive divergence as an essential source of diversity. The role played by ecological processes in structuring species, and population has, however, remained to be contentious. It is through disruptive selection for differing habitats and resources that adaptive radiations have evolved. While in sympatry, reinforcement is driven by hybridization, when it comes to allopatry, both reinforcement and hybridization would not be present. By contrasting population divergence in allopatry and sympatry, valuable insight into the nature of these processes can be provided.

To some extent, therefore, the idea of species is quite intuitive. After the recolonization of glaciated habitats, the adaptative radiations become quite common in several temperate aquatic species. As a result, morphologically bimodal populations erupt, and they appear to have a huge phenotypic divergence. Such radiations are often associated with divergent ecological or trophic strategies like those observed in limnetic and benthic stickleback.

Conclusion

Examining the nature of the derived bimodal population in allopatry and sympatry suggests that the levels of genetic and morphological divergence have significant isolation and adaptive morphological divergence under sympatry and allopatry. There are, however, certain characteristics that indicate a great divergence in sympatry. Hybridization in sympatry is faced by a partial barrier indicating the importance of reinforcement through prezygotic incompatibilities. Moreover, the partial barriers also suggest gene flow are possible, and changes at the contemporary selections might impact the stability and allow significant hybridization and introgression (Bradbury et al., 2010). The evolutionary dynamics responsible for the production of isolation and divergence have a significant difference between sympatry and allopatry though the final result could be the same. While the result might have some similarities, the process involved the formation of stability, and divergence in sympatry has a likelihood to differ greatly from allopatry. That can hence pose some management and conservation challenges.

Reference

Kang, L., Garner, H. R., Price, D. K., & Michalak, P. (2017). A Test for Gene Flow among Sympatric and Allopatric Hawaiian Picture-Winged Drosophila. Journal of Molecular Evolution, 84(5-6), 259-266.

Savolainen, V., Anstett, M. C., Lexer, C., Hutton, I., Clarkson, J. J., Norup, M. V., ... & Baker, W. J. (2006). Sympatric speciation in palms on an oceanic island. Nature, 441(7090), 210-213.

Bradbury, I., Coulson, M., Cook, A., & Bentzen, P. (2010). Evidence for divergence and adaptive isolation in post-glacially derived bimodal allopatric and sympatric rainbow smelt populations. Biological Journal Of The Linnean Society, 101(3), 583-594. h
ttps://doi.org/10.1111/j.1095-8312.2010.01533.x.