Figure 2
From: Morphological differentiation despite gene flow in an endangered grasshopper
Alternative hypotheses. Alternative hypotheses to explain the relationship between morphological differentiation and gene flow in this study of grasshoppers in New Zealand. Two morphologically defined species exist that have a common ancestor and may share identical alleles due to decent, but as distinct species derived alleles are also expected. (a) An abrupt speciation event is expected to result in accumulation of distinct traits and genotypes, including at neutral loci. (b) Sharing of neutral genetic alleles might be maintained by ongoing gene flow whilst alleles at some loci are subject to selection. Morphological difference is an observable expression of genetic loci under diverging selection. (c) Hybridisation or reticulation is expected to result in individuals with intermediate forms.