Reef fishes and many other marine species live all their adulthood in one place but early in their lives, when they're eggs and larvae, spend a short period of time drifting and swimming in the open ocean. It seems intuitive that the duration of this open water period should determine the geographic extent over which species are found as species that spend longer drifting at sea are likely to reach greater distances. Interestingly enough, numerous studies have consistently failed to find any relationship between the duration of the open water period and the geographic coverage of marine species. A new research paper has uncovered this mystery.
"One of the most puzzling results in the study of reef fishes and other marine organisms that dwell sea-floor habitats as adults but drift in open water early in their lives is why their geographic coverage bears no relationship with the duration of the open water period," explains co-author Dr. Camilo Mora, post-doctoral fellow in the Department of Biological Science at Dalhousie University. "Since this idea was first proposed over 30 years ago, we've been scratching our heads trying to resolve this mystery by evaluating the relationship multiple times in different groups of species and regions. Yet we consistently we failed to find a noteworthy relationship."
In this new study, the team of researchers, which included marine ecologists, geneticists and ocean current modelers, first evaluated the possibility that the relationship between geographic extent and the duration of the open water period was compounded by the evolutionary age of species, whose effect has not been considered in previous studies. The rationale was that the age of a species should add to the geographic coverage of species as older species have had more time to expand geographically compared to younger species.
To evaluate this idea, the authors compiled the largest set of data yet assembled on evolutionary ages of reef fis
|Contact: Dr. Camilo Mora|