Morphs Of Species Research Articles

A new morph of Telmatochromis temporalis (Cichlidae; Cichliformes) from Lake Tanganyika

Telmatochromis temporalis is a cichlid fish endemic to Lake Tanganyika. Two morphs of this species, normal and dwarf, form a good model for the study of ecological speciation through divergent natural selection on body size. This study reports a third morph of this species, slender morph, which was collected from deep waters off Kasenga, Zambia, whereas the normal morph inhabits shallow waters of the same locality. This study examined morphological characters and mitochondrial DNA sequences in 18 populations of the three T. temporalis morphs and two closely related species. The slender morph was morphologically similar to the normal and dwarf morphs of the same species, but clearly differed from closely related species. Genetic analyses showed that the slender morph was closest to but significantly different from the parapatric normal morph, suggesting reproductive isolation between them. Due to the lack of colour differences between morphs and of obvious geographical barriers between habitats, reproductive isolation between these morphs may be attributed to ecological factors, rather than sexual or geographical segregation. Further studies examining the evolution of the slender morph may deepen our knowledge of initial stages of speciation, like in the dwarf morph.

Reduced recombination in gynodioecious populations of a facultative apomictic orchid

Many plants combine sexual reproduction with some form of asexual reproduction to different degrees, and lower genetic diversity is expected with asexuality. Moreover, the ratios of sexual morphs in species with gender dimorphism are expected to vary in proportion to the reproductive success of the sexual process. Hence, sex ratios can directly influence the genetic structure and diversity of a population. We investigated genotypic diversity in 23 populations of a facultative, apomictic gynodioecious orchid, Satyrium ciliatum, to examine the effect on genotypic diversity of variation in the frequency of females and in the amount of sexual reproduction. The study involved one pure female, seven gynodioecious (both females and hermaphrodites present) and 15 hermaphroditic populations. Pollinia receipt was higher in hermaphroditic than in gynodioecious populations. Analyses of variation in ISSRs demonstrated that genotypic diversity was high in all populations and was not significantly different between hermaphroditic and gynodioecious populations. We used character compatibility analysis to determine the extent to which recombination by sexual reproduction contributed to genotypic diversity. The results indicate that the contribution of recombination to genotypic diversity is higher in hermaphroditic than in gynodioecious populations, consistent with the finding that hermaphroditic populations received higher amounts of pollinia. Our finding of reduced recombination in gynodioecious populations suggests that maintenance of sex in hermaphrodites plays an important role in generating genotypic diversity in this apomictic orchid.

Effects of Five Insecticides on the Probing, Walking, and Settling Behavior of the Green Peach Aphid and the Buckthorn Aphid (Homoptera: Aphididae) on Potato

From 14 to 26% of apterous green peach aphids, Myzus persicae (Sulzer), placed on leaflets of potato treated with deltamethrin, fenvalerate, pirimicarb, and methamidophos dispersed to untreated leaflets, compared with only 2-6% of aphids placed on control or dimethoate-treated leaflets. Apterous buckthorn aphids, Aphis nasturtii (Kaltenbach), dispersed significantly in greater numbers only from deltamethrin and fenvalerate treatments. Pyrethroids reduced duration of probing for alate and apterous morphs of both species from 33 to 77%. Dimethoate decreased probing of apterous A. nasturtii 24%, while methamidophos did not alter probing times for apterous or alate morphs of either species. Pirimicarb reduced probing times of M. persicae , and the results indicated that the effect on probing may depend on the condition of the leaf material or species of aphid. Colonization of pyrethroid-treated and untreated leaf disks in flight tests suggests no repellent action on M. persicae . Decreased probing on pyrethroid-treated leaves could help control the spread of nonpersistent viruses, but increased dispersal of aphids might decrease the effectiveness of control. These data extend the behavior-modifying properties of pyrethroids to A. nasturtii and confirm that nonpyrethroid insecticides can affect the behavior of certain aphid species.