curve

2026 Alfakih The Geographical Variation of Colour Change in the Arabian Killifish (Aphaniops dispar Sensu Lato) From Freshwater and Marine Ecosystems Widely distributed animals may exhibit substantial plastic physiological, morphological and behavioural responses to environmental changes. One such extraordinary form of plasticity is colour change, which varies substantially among most taxonomic groups. Most studies on colour change have focused on a single population, which has left a gap in our knowledge of colour change variation between populations. Examining colour change variation across populations of a taxon can shed light on how it evolves. Colour plasticity is influenced by spatial and temporal contextual variables, including visual habitat heterogeneity, predator diversity and their interaction. Using the Arabian killifish (Aphaniops dispar sensu lato) as a model, we examined the geographical variation of colour change in two freshwater and two marine populations from the west of Saudi Arabia, separated by vicariant and distance barriers and that differed in habitat visual characteristics and potentially in predator diversity. We used digital photography and visual modelling to investigate the ability of individuals in each of the populations to change colour when presented with achromatic (black and white) and chromatic (beige, brown and green) backgrounds. When presented with a black background, we found that individuals in all populations were capable of becoming darker at varying rates, but in a similar manner. Becoming lighter was more challenging, with individuals from all populations changing less on white than on black backgrounds and with one freshwater population exhibiting almost no response. However, there were complex interpopulation differences in chromatic responses, with marine populations exhibiting generally greater responses to the given backgrounds than freshwater populations. Here, we discuss the evolutionary and ecological factors possibly underlying these variations and their repercussions.

2026 Yinpeng Cryptic species are widespread across vertebrates Many species delimited by morphological data contain two or more species that are distinct based on molecular data (i.e. cryptic species). Cryptic species have important implications for ecology, evolution and conservation. For example, morphology-based species of limited conservation concern can contain cryptic species that are in imminent danger of extinction. Here, we examined the prevalence of cryptic species across vertebrates. We also examined the controversial use of mitochondrial data, and whether they overestimate or underestimate cryptic species relative to nuclear data. We obtained usable estimates of species limits from 373 studies. We found that each morphology-based species contained approximately two cryptic species on average. This number was surprisingly similar across major groups despite dramatic differences in ecology and physiology (fishes versus birds), and similar to comparable estimates in insects. Cryptic species numbers from mitochondrial data alone were often higher than from nuclear data, but were generally not statistically different. Overall, our results show that cryptic species are numerous and widespread across vertebrates. These results suggest that cryptic species should not be ignored in analyses of species richness, speciation and extinction in living and fossil organisms. Furthermore, testing for cryptic species across morphology-based vertebrate species should be an urgent priority for conservation.

00-0-Copr_2025-Ateah_Alfakih.jpg
xs sm med lg xlg