Abstract
Wang et al. in this journal argue that it may be time to abandon a classic idea about species, the biological species concept (BSC), given recent findings with genomic data on closely related taxa. Furthermore, they propose a set of tests on genetic or genomic data that might lead to acceptance or rejection of the biological species concept. Wang et al. are not the first to critique the biological species concept (BSC), which has survived an onslaught of attacks from many fronts. What is the biological species concept? And what is the new critique about? In this commentary, I briefly cover the history of ideas about biological species, then discuss current work that depends on rich, genome-scale sequence data, before attempting to resolve issues.
Highlights
Wang et al are not the first to critique the biological species concept (BSC), which has survived an onslaught of attacks from
‘There is a tendency in the integrated gene complex to establish an ever greater cohesion, to achieve a steady improvement of developmental and of genetic homeostasis...,’ and ‘Speciation is potentially a process of evolutionary rejuvenation, an escape from too rigid a system of genetic homeostasis’
The authors review existing literature for gene flow among named species, and while acknowledging its existence, they say ‘we find no case of large scale introgression in late stages of speciation, when postmating reproductive isolation is evident.’
Summary
The term ‘biological species concept’ (BSC) was coined originally by Ernst Mayr, building on Dobzhansky’s ideas of reproductive isolation [2,3,4] during the later phases of the ‘Modern Synthesis’ between Darwinian evolution and Mendelian genetics. Mayr clearly recognized this: as we have seen, he believed that gene flow and the lack of reproductive isolation among populations hindered evolutionary progress and prevented speciation. In his view, speciation was ‘complete’ when there was a complete absence of successful gene flow To solve the issue of the slow rate of divergence demanded by his view of species as optimized ‘delicately integrated genetic systems,’ Mayr popularized another idea, that small populations dispersing to geographically separated locations could speciate more rapidly by means of the ‘founder effect’, leading to a ‘genetic revolution’ via rapid reorganization of coadapted gene complexes [4,9]. Today the founder effect is deemed poorly supported by theory or data, while the more general idea that allopatric speciation is the norm still holds some sway [6,10,11,12]
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