Mitochondrial DNA sequences of various species of the genus Equus with special reference to the phylogenetic relationship between Przewalskii's wild horse and domestic horse

The noncoding region between tRNA^Pro and the large conserved sequence block is the most variable region in the mammalian mitochondrial DNA D-loop region. This variable region (ca. 270 bp) of four species of Equus, including Mongolian and Japanese native domestic horses as well as Przewalskii's (or Mongolian) wild horse, were sequenced. These data were compared with our recently published Thoroughbred horse mitochondrial DNA sequences. The evolutionary rate of this region among the four species of Equus was estimated to be 2–4 × 10^–8 per site per year. Phylogenetic trees of Equus species demonstrate that Przewalskii's wild horse is within the genetic variation among the domestic horse. This suggests that the chromosome number change (probably increase) of the Przewalskii's wild horse occurred rather recently.Correspondence to: N. Ishida     

Constant morphological patterns in the hemolymph vascular system of crayfish (Crustacea,Decapoda)

We present a study of the hemolymph vascular system of the marbled crayfish, Procambarus fallax f. virginalis, the only crayfish species known to be parthenogenetic. To identify potential evolutionary patterns, we compared data from a total of 48 specimens of P. fallax with 22 specimens of Orconectes limosus. Visualizations (2D and 3D) were carried out using a combination of classical and modern morphological techniques. Our data were compared to the existing literature.Like all Decapoda, both P. fallax and O. limosus have a hemolymph vascular system, consisting of a globular heart with seven off-branching arteries. We were able to visualize in detail the heart of crayfish for the first time, i.e., the myocard with its clusters of muscles running through the lumen of the heart, the valves and flaps of ostia and arteries. Furthermore, the branching patterns of the seven artery systems were analyzed. Anatomical structures identified to be consistent in all specimens of both species were combined as ground pattern of hemolymph vascular system features for Astacida.     

Selective Pressures on RNA Hairpins In Vivo and In Vitro

Comparison of the most stable potential hairpins in the sequences of natural ribozymes with those in the randomized sequences has revealed that the hairpin loop energies are lower than expected by chance. Although these hairpins are not necessarily parts of functional structures, there is a selective pressure to diminish the destabilizing free energies of the hairpin loops. In contrast, no significant bias is observed in the stacking values of the most stable stems. In the ribozymes isolated in vitro the loops of potential hairpins are closer to random values, which can result in less efficient folding rates. Furthermore, the effects of kinetic traps seem to be more significant in the folding pathways of the in vitro isolates due to a potential to form stable stacks incompatible with the functional folds. Similarly to natural ribozyme sequences, the untranslated regions of viral RNAs also form hairpins with relatively low loop free energies. These evolutionary trends suggest ways for efficient engineering of improved RNA constructs on the basis of analysis of in vitro isolates and approaches for the search of regions coding for functional RNA structures in large genome sequences. Received: 12 January 2001 / Accepted: 21 May 2001     

Evolution of Plant-Like Crystalline Storage Polysaccharide in the Protozoan Parasite Toxoplasma gondii Argues for a Red Alga Ancestry

Single-celled apicomplexan parasites are known to cause major diseases in humans and animals including malaria, toxoplasmosis, and coccidiosis. The presence of apicoplasts with the remnant of a plastid-like DNA argues that these parasites evolved from photosynthetic ancestors possibly related to the dinoflagellates. Toxoplasma gondii displays amylopectin-like polymers within the cytoplasm of the dormant brain cysts. Here we report a detailed structural and comparative analysis of the Toxoplasma gondii, green alga Chlamydomonas reinhardtii, and dinoflagellate Crypthecodinium cohnii storage polysaccharides. We show Toxoplasma gondii amylopectin to be similar to the semicrystalline floridean starch accumulated by red algae. Unlike green plants or algae, the nuclear DNA sequences as well as biochemical and phylogenetic analysis argue that the Toxoplasma gondii amylopectin pathway has evolved from a totally different UDP-glucose-based metabolism similar to that of the floridean starch accumulating red alga Cyanidioschyzon merolae and, to a lesser extent, to those of glycogen storing animals or fungi. In both red algae and apicomplexan parasites, isoamylase and glucan–water dikinase sequences are proposed to explain the appearance of semicrystalline starch-like polymers. Our results have built a case for the separate evolution of semicrystalline storage polysaccharides upon acquisition of photosynthesis in eukaryotes.This article contains online-only supplementary material.Reviewing Editor:Dr. Patrick Keeling     

Kinship,sex, and fitness in a Caribbean community

Patterns of human kinship commonly involve preferential treatment of relatives based on lineal descent (lineages) rather than degree of genetic relatedness (kindreds), presenting a challenge for inclusive fitness theory. Here, we examine effects of lineage and kindred characteristics on reproductive success (RS) and number of grandchildren for 130 men and 124 women in a horticultural community on Dominica. Kindreds had little effect on fitness independently of lineage characteristics. Fitness increased with the number of lineal relatives residing in the community but decreased beyond an apparently optimal lineage size, suggesting resource enhancement and competition among kin. Female-biased patrilineage sex ratio was positively associated with men’s fitness, while male-biased matrilineage sex ratio was positively associated with women’s fitness. Number of brothers in the community was negatively associated with men’s, but not women’s, fitness. Parents and number of sisters had no effect on either male or female reproduction; however, women with younger sisters had higher RS, suggesting benefits of kin support for childcare. In sum, imposed norms for lineage social organization may enhance lineal ancestors’ inclusive fitness at a cost to individual inclusive fitness. Research was supported by grants from the National Science Foundation (BNS 8920569 and SBR 9205373); the University of Missouri Research Board to MVF; the Earthwatch Center for Field Research to MVF, Marsha B. Quinlan, and RJQ; and the B.S.U. Center for International Programs and Office of Academic Research and Sponsored Programs to RJQ. Marsha Quinlan and Napoleon Chagnon provided valuable advice on earlier drafts. Ed Hagen gave generous help with Descent software for kinship analysis. Many friends, teachers, and consultants in Bwa Mawego contributed generously to this study: the Durand clan—Juranie, Jonah, Elford, Induria, Margelia, Eugenia, Lillia, Elquimedo, Zexia, Delfine, Wilford, Nathalie, and Sarah; the Warringtons—Martina, Amatus, Onia, Belltina, Zabius, Sarah-Gene, and Heckery; the Laudats—Eddie, Benedict, and Dellie; the Laurents—Aron and Tito; the Lewises—Eddie, Melanie, Eulina, Spliffy, Ganjala, Julina, Jalina, and Marietta; Franklin Vigilante; Lawrence Prosper; Edmund Sanderson; Alex and Tita Alie; and especially Mistress Didi and Mr. McField Coipel. Rob Quinlan is Assistant Professor of Anthropology at Ball State University. His main interests include human evolutionary ecology, reproductive development, parental care, kinship, and medical anthropology. He has conducted fieldwork in Dominica since 1993. Mark Flinn is Associate Professor of Anthropology and Psychological Sciences at the University of Missouri-Columbia. His main interests include evolutionary theory, childhood stress, family relationships, and health. He has conducted fieldwork in Dominica every year since 1987.     

Evolutionary trends of the hairy-faceSaguinus in terms of the dental and cranial morphology

Shape variations in the dentition and the cranium were analyzed for sevenSaguinus forms of the hairy-face tamarin by applying the factor analysis method. The results obtained for the dental and cranial measurements were almost consistent with each other. The magnitude of the difference in shape factors between theS. nigricollis group and theS. midas group is appreciably larger than that between the former group and theS. mystax group. If the ancestral geographic centre of origin is postulated as being within the region which is inhabited by the livingS. nigricollis group, the morphological distances between any pairs of groups correlate well with the geographic distances between them. Concerning the dental and cranial morphologies, the physical changes in the three species group probably took place in two directions; that is, from theS. nigricollis group to theS. mystax group, and from theS. nigricollis group to theS. midas group. The forms belonging to each species group are more closely related to each other, with the exception ofS. imperator in theS. mystax group. The uniqueness ofS. imperator was clearly demonstrated by factor analysis and distance analysis. In theS. mystax group, although still hypothetical,S. imperator may have been related only through the basic ancestral stock toS. labiatus andS. mystax.     

From robustness to resilience: A network Price identity approach

We model a closed-loop network of agents distributed among subnetworks and study the sustainability of network structures in presence of random perturbations. The model outcomes show that the stability of compartmentalized networks built on uniform operators depends on perturbations on between-subnetwork coupling, while the stability of networks built on mutation operators depends on their assimilation capacity. Through the study of eigenvalues of the Laplacian, we succeed in measuring the degree of network robustness and resilience. Our results also permit to situate the Price theorem, both in its standard and expanded forms, in the context of network evolutionary variational identity.     

Seven types of adaptationism

Godfrey-Smith (2001) has distinguished three types of adaptationism. This article builds on his analysis, and revises it in places, by distinguishing seven varieties of adaptationism. This taxonomy allows us to clarify what is at stake in debates over adaptationism, and it also helps to cement the importance of Gould and Lewontin’s ‘Spandrels’ essay. Some adaptationists have suggested that their essay does not offer any coherent alternative to the adaptationist programme: it consists only in an exhortation to test adaptationist hypotheses more thoroughly than was usual in the 1970s. Here it is argued that the ‘Spandrels’ paper points towards a genuinely non-adaptationist methodology implicit in much evolutionary developmental biology. This conclusion helps to expose the links between older debates over adaptationism and more recent questions about the property of evolvability.

Evolutionary matrix games and optimization theory

An evolutionarily stable strategy (ESS) is only required to be capable of resisting invasion by rare mutant strategies. In contrast, an absolute invader strategy (AIS) is a rare mutant strategy that can invade any established strategy. We show that the predictions of the outcome of evolution made by optimization models are compatible with those made by the classical expected payoff comparisons in matrix games. We also show that if a matrix game has an AIS that AIS is unique and is also an ESS. But an ESS need not be an AIS. In pure-strategy submodels, an AIS need not be unique. An AIS of a matrix game has global asymptotic stability property in the game dynamics which involve only pure strategies including the AIS.     

The effect of volcanism on postglacial migration and seed dispersal. A case study in southern South America

During the Quaternary, southern South American temperate forests were confined to small and isolated refugia. Recolonization could be related not only with location of refugia but also with postglacial phenomena like volcanism, which could have interrupted the expansion of the forests. The aim of this study was to analyze the local effect of volcanism during the postglacial migration of Nothofagus nervosa in a particular region of Argentina were convergence of two migratory routes was suggested. The main question is whether admixture occurred or not and if the current populations are connected by pollen or seed gene flow. Two populations separated by a 3-km-width lava flow were sampled. Buds from 30 individuals of each of the two populations and from a total of 142 juveniles were analyzed. Genetic variation was detected through maternally inherited chloroplast deoxyribonucleic acid (cpDNA; polymerase chain reaction restriction fragment length polymorphisms of two fragments) and nuclear markers like isozymes (six loci) and simple sequence repeats (three loci). Population genetic parameters were estimated and the existence of a genetic structure was tested with an analysis of molecular variance. Historical gene flow was estimated through the indirect method of the genetic differentiation (F _ST). Chloroplast DNA revealed a total genetic differentiation between the two populations indicating completely isolation respecting seed gene flow. On the contrary, the degree of genetic differentiation for the nuclear markers was significantly lower, and moderate levels of historical gene flow through pollen were inferred. The results suggest that in this area, volcanism has played an important local role during the expansion of N. nervosa maintaining these two populations separated. Communicated by A. Kremer