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Transcript
;;;;;;;;;;;;;;;;;;;;;; Beak of the Fish: What Cichlid Flocks Reveal About Speciation Processes East African Great Lakes and Their Cichlid Flocks by Holly Jessop 2 Introduction 2 those fourteen different species of birds continues to different species has been instructive, then an fish have evolved thousands of new species within species that have also emanated from one cichlid confined to the surface layers and shallow benthic Cichlid Species: A Kaleidoscope of Form and Color within the cichlid family provides an opportunity to reminiscent of aquaria with swarms of colorful fish in differently colored fish morphs of the same or used to further uncover the detail in the processes 16 characteristics have recently provided an additional means by which cichlid diversification can be That is, their classification as separate species was were derived from different ancestral lines, and in repeatedly shown that these cichlid radiations have Origins: Out of Lake Tanganyika Comes Explosive, Rapid, and Parallel Evolution Placidochromis from the fleshy lips of the Lobochilotes Placidochromis are more closely related none of these cichlid species are shared between inter-related becomes an important initial step in proven to be the most useful tool for this detective different species separately evolved the same tooth cichlids are the ancestors from which the cichlids in independently evolved within different parts of unrelated, but separately evolved the same color source reveals that speciation processes within these Multistage Evolutionary Patterns The frequent occurrences of parallel evolution over twice the number of mitochondrial base pairs and ten times the number of species, confirms that that they had sampled only 24 of the 200 species of 17 This division is then followed by diversification in differences in color and other communication-related Speciation Process Stage 1: Division of Habitat of competitive interspecific influences, early cichlids adapted to the benthic sand habitat, while others adapted to the other available benthic substrate that evolutionary history is well supported by cichlid Pseudotropheus species have a mouth that is somewhat Speciation Process Stage 2: Division of Food Resources Labeotropheus that if early speciation processes were not driven by Labeotropheus mouths are adaptations that increase the efficiency Metriaclima cichlids these species first occurred as a result of trophic possible food sources, which is reflected in both their description of cichlid speciation processes that methodically sift the bottom for detritus, while birds, males will construct and then defend towers are free to select any sandcastle territory, and its success also increases as a function of coloration in cichlid speciation involves numerous divisions, all based on colors and behaviors that communicate do not limit their predation to conspecifics, as many Similar Speciation Processes in Other Vertebrates speciation also successfully describes patterns Speciation Process Stage 3: Division via Communication diversified first into bottom- versus water column- the differences are most notable in male secondary to select not only the best male, but also to select a have physically shaped and diversified cichlids, the found in the Anolis Anolis comes from a number of different islands where they evolved But Why So Many More Cichlids? While evolutionary scientists have made evolutionary mechanisms responsible for the uniquely 19 to this question continues to evade theorists, but Additional clues to the mechanisms of evolution in cichlids have recently been provided by studies The overall cichlid body plan tends to be crucial role in cichlid speciation, discovery of the increase the numbers and types of food items that Labeotropheus fuelleborni Metriaclima zebra this structure mostly aids directional movement of were intermediate to that present in the parents, diet to molluscs, suction up snails with their outer the spread in frequency becomes wider in the F2 may have unveiled one means by which cichlids diversified so numerously and rapidly in response to of every possible food resource, and so to radiate 20 and reflection on a more macroscopic-scale are also diversification in cichlids, then the amino acid substitutions should have occurred more frequently in cichlids than finches, despite so many similarities in the mechanisms involved in their speciation, acid substitutions should be similar in these cichlids Bmp4 found that the rate of amino acid substitutions in Bmp4 Bmp4 speciation rates level off, some species out-compete role of Bmp4 is also evident from comparisons of cichlids to protein domain areas affected by these numerous amino acid substitutions in the Bmp4 found that all substitutions affected the portion of the protein responsible for post-translational control of the Bmp4 Bmp4 Disappearing Cichlids recently been found that the Bmp4 important role in the cranio-facial development of Bmp4 of the principal molecular variables that provided comparisons of Bmp4 there with seventy-five percent of their animal factors involved in the control and modification of Similarly, the introduction of commercial methods of a decline in cichlid catch after only twenty years 21 Conclusion cichlids are also valued by the aquarium trade and speciation are evident in cichlids at small scales, this practice will undoubtedly disrupt cichlid population has caused rapid eutrophication and increased perhaps thousands of spectacularly colored fish will Figures ability to properly perceive color was interfered with, females mated indiscriminately with males of many for observed decreases in cichlid species diversity Figure 1: Great Lake Cichlids Are Monophyletic and Derived from Lake Tanganyika Flocks. After Meyer et al. (1990). 22 Figure 2: Similar Cichlid Forms Evolved Independently and Convergently. From Albertson & Kocher (2006). Figure 3: Cichlid Outer Jaw Flexibility and Pharyngeal Jaw Apparatus: Key Innovations. From Barlow (2000). Figure 4: Head, Jaw, and Dentition Differences Between Two Cichlids. From Albertson & Kocher (2006). 305 60 Heredity 97 19 102 Evolution 40 94 2 96 inferred from parallel radiations in nuptial 100 20 22 evolutionary processes in East African cichlid 8 10 347 Fisheries 6 88 267 273 of the USA 96 24 Bmp4 5 19 10 51 300 277 18 for a literature review of contemporary scientific 56 53