Species, speciation... and definitions

What exactly is a species? Humans are obsessive with the categorization of the world around us. However, we often encounter that the world is not as easy to catergorize as one would expect. This is no different for how we group organisms as a species and their evolutionary relationships to one another. There are many systems that can be used for this, first being the biological species concept. The biological species concept is defined as a group of organisms that can naturally reproduce between each other and they are isolated from other populations. This provides a boundary based on reproductive isolation and explains how speciation occurs through gene flow interruption. This, however, does not explain asexual organisms, hybridization, or ring species. Next, is the morphological species concept where physical characteristics and phenotypes are take into consideration for defining a species. This concept can account for asexual organisms and can organize populations aside from genetic information. The challenges for the morphological species concept are that species can vary widely and it may be difficult to narrow down specific phenotypes, cryptic species, and convergent evolution. The ecological species concept, however, is defining a species based on the ecological niche they occupy. This can showcase how organisms adapt to different environments and their role in an ecosystem. Although, this can limit how organisms are different when they may overlap in their niche, and this may not determine the subtle differences between species. Lastly, the phylogenetic species concept focuses on evolutionary relationships established using genetic data, this locates the most recent common ancestor. This can account for genetic divergence, and works well in organisms with primarily genetic data to tell the difference. There may be some excessive isolation of organisms that share a certain level of genetic variance, but this requires an extreme amount of phylogenetic information that may not be available. How does this ambiguity in defining species impact our understanding of biodiversity and evolution? Mostly, how we define a species can impact how prioritized different species may be in terms of conservation. For evolution, this can influence how we understand evolutionary relationships and what characteristics should be weighed more heavily to establish whether something is a different species and where relatedness occurs. It is clear that defining a species is a complex task, and there is likely no one correct answer. So a definition of what a species lies within accounting for which concept applies for the task at hand. It may help to understand biodiversity to begin with understanding which organisms are an individual species, but that is up to us to decide.