Morphological differences between species often involve changes at multiple genetic loci, as revealed by F2 quantitative trait locus (QTL) mapping (e.g., Alpert et al. 1995, Orr 2001, Gadau et al. 2002).
In addition, most dinosaurs are known solely from bones and can only be evaluated from a morphological standpoint, whereas extant species often have very similar skeletal morphology but differ in other ways which would not normally be preserved in the fossil record, such as behavior, or coloration.
Resource competition between sympatric species can produce morphological differences between those species, often resulting in ecological divergence.
Different morphological groups of Helichrysum species often display unique qualitative and quantitative chemical compositions [ 5].
Some of the most striking information has come from the discovery that different morphological types of some single species (often referred to as morphs) arise following interactions with individuals of other species.
However, the subtle morphological characters that separate closely related species often demand expert interpretation (e.g. [1]), forcing studies to either limit their taxonomic scope, or to only identify specimens to a higher taxonomic category (e.g. family, genus).
As a tool to understand the evolutionary history of members of this genus, closely related species are often placed in morphological species groups (e.g., [ 1, 6]).
Most eukaryotes remain undescribed and the entry of a species into the Linnaean system does little to ensure its subsequent recognition because the subtle morphological characters that separate closely allied species often demand expert interpretation.
Because body shape has a high degree of conservation in this genus, morphological species discrimination by Kullander and Ferreira was often based on subtle color pattern differences, modal differences in meristic variation, and geography [ 25] (see also Methods).
However, plant species often exhibit contrasting photosynthetic and morphological responses to altitude.
