Irv Kornfield

Polygynandry inPseudotropheus zebra, a cichlid fish from Lake Malawi

SynopsisParental care in the Malawian cichlid fishPseudotropheus zebra ‘BB’ is extensive and exclusively maternal; males contribute only genetic material. The costs of searching for multiple mates (in this case risk of predation on orally incubated eggs) suggested that females should be monandrous; microsatellite genetypes of seven brooding females and their young, however, reveal extensive multiple paternity in this species, with a mean of 3.8 paternal individuals per brood. Polygynandry inP. zebra is probably not maintained by selection for genetically diverse offspring; potential explanations include avoidance of inbreeding, and bet-hedging on other male characteristics that females are unable to evaluate when selecting a mate. The observed degree of multiple paternity strongly suggests that females are free to choose mates as they will, a prerequisite of many theories positing sexual selection as a key element in Malawi chichlid evolution. It should also result in elevation of effective population sizes, and thus be antagonistic to runaway evolution of male secondary sexual characteristics, but not necessarily to other modes of sexual selection.

Hybrid origin of a cichlid population in Lake Malawi: implications for genetic variation and species diversity

The importance of species recognition to taxonomic diversity among Lake Malawi cichlids has been frequently discussed. Hybridization — the apparent breakdown of species recognition — has been observed sporadically among cichlids and has been viewed as both a constructive and a destructive force with respect to species diversity. Here we provide genetic evidence of a natural hybrid cichlid population with a unique colour phenotype and elevated levels of genetic variation. We discuss the potential evolutionary consequences of interspecific hybridization in Lake Malawi cichlids and propose that the role of hybridization in generating both genetic variability and species diversity of Lake Malawi cichlids warrants further consideration.

Evolution of the mitochondrial DNA control region in the mbuna (Cichlidae) species flock of Lake Malawi, East Africa.

Considerable controversy has surrounded the application of mitochondrial DNA data to reconstruction of evolutionary relationships among the endemic cichlids of Lake Malawi. Central to this debate has been the issue of whether lineage sorting is complete, and thus whether these data actually reflect species phylogeny, or simply gene genealogy. Review of all mtDNA control region sequences available for members of one monophyletic subset of this species flock, the Malawi rockfishes, or mbuna, strongly indicates that lineage sorting is incomplete: Character-based analyses of these sequences reconstruct gene, not species, interrelationships. Analysis of the pattern of nucleotide substitutions differentiating these mtDNA alleles suggests that pyrimidine residues undergo transition substitutions more often than do purines. Estimation of the magnitude of derived sequence differentiation in light of the reconstructed gene genealogy suggests that the mbuna may be of considerably more recent vintage than previous molecular characterizations have indicated.

Sexual selection, reproductive behavior, and speciation in the mbuna species flock of Lake Malawi (Pisces: Cichlidae)

The cichlid species flocks of the African Great Lakes represent the most extreme case of adaptive radiation among vertebrates. Recently, attention has focused on the potential for sexual selection to drive or accelerate speciation in these fishes. Cichlids as a whole are social in nature and display complex behavior, particularly during courtship and spawning; however, the extent to which changes in species recognition cues may account for species diversity among haplochromine lineages has remained speculative. Our investigations have indicated that oral incubating haplochromines show a reduction in diversity and extent of courtship relative to substrate brooding cichlids, and apparently retain aspects of a primitive specific mate recognition system. Laboratory observations of courtship in the Malawian endemicPseudotropheus zebra suggest that organization of the spawning bout is loose, and lacking in any well defined stimulus-response chain. Interspecific comparisons of in situ courtship behavior among male mbuna, lithophilous haplochromines of Lake Malawi, revealed only one potential example of species-specific behavior, and indicated that mate choice occurred prior to the onset of intense courtship. Courtship display by male mbuna does not appear critical to species recognition and may represent an evolutionary relict. Alternatively, male courtship display may have an indirect effect on successful reproduction or may be maintained through pleiotropic effects. The mbuna display no evidence of behavioral innovation and show limited interspecific differentiation in behavioral expression. More generally, there is no evidence at present to suggest that epigamic sexual selection, acting on courtship behavior, has been a major mechanism in the diversification of the haplochromine species flocks.

MOLECULAR PERSPECTIVE ON EVOLUTION AND ZOOGEOGRAPHY OF CYPRINODONTID KILLIFISHES (TELEOSTEI; ATHERINOMORPHA)

Phylogenetic relationships among 16 cyprinodontid species representing nine genera were inferred from mitochondrial DNA sequence data and compared to hypotheses inferred from anatomical morphology. Cladistic analysis of 16s rRNA and control region sequences strongly supported monophyly of the Andean genus Orestias and of the Mediterranean cyprinodontids Aphanius and Kosswigichthys. Cladistic analysis also supported a sister-group relationship between these two geographically disjunct clades. Additional sister-group relationships between Aphanius dispar and A. mento, Orestias luteus and 0. ispi, Jordanella pulchra and Floridichthys carpio, and the genera Cyprinodon and Megupsilon were supported by sequence data. In general, morphological characters that are unique within cyprinodontiformes are concordant with our results; those that are convergent for several lineages are not. Zoogeographic analysis of this phylogeny suggests a Tethyan distribution for the ancestral cyprinodontid lineage. Range expansion, permitted by the formation of epicontinental seas in the Cretaceous, may explain the presence of Orestias, most closely related to the Mediterranean Aphanius, in Andean South America.

Phylogeography of Lake Malawi cichlids of the genus Pseudotropheus : significance of allopatric colour variation

One of the most compelling features of the cichlid fishes of the African Great Lakes is the seemingly endless diversity of male coloration. Colour diversification has been implicated as an important factor driving cichlid speciation. Colour has also been central to cichlid taxonomy and, thus, to our concept of species diversity. We undertook a phylogeographical examination of several allopatric populations of the Lake Malawi cichlid Pseudotropheus zebra in order to reconstruct the evolutionary history of the populations, which exhibit one of two dorsal fin colours. We present evidence that populations with red dorsal fins (RT) are not monophyletic. The RT population defining the northern limit of the distribution has evidently originated independently of the southern RT populations, which share a common ancestry. This evidence of species–level colour convergence is an important discovery in our understanding of cichlid evolution. It implies that divergence in coloration may accompany speciation, and that allopatric populations with similar coloration cannot be assumed to be conspecific. In addition to this finding, we have observed evidence for introgression, contributing to current evidence that this phenomenon may be extremely widespread. Thus, in species–level phylogenetic reconstructions, including our own, consideration must be given to the potential effects of introgression.

Molecular systematics of the Acoela (Acoelomorpha, Platyhelminthes) and its concordance with morphology.

The phylogenetic relationships of the lower worm group Acoela were investigated using newly obtained nuclear 18S rDNA sequences from 16 acoels in combination with 16 acoel sequences available on GenBank from other laboratories. Parsimony and maximum likelihood analyses of the molecular data supported the concept that the Acoela is monophyletic; however, the gene tree produced by these analyses conflicts with the current taxonomic system for the Acoela in several family-level groupings. Most notable is the apparent polyphyly of the largest family of acoels, the Convolutidae. DNA analysis grouped together species of small-bodied convolutids in one clade, while large-bodied convolutids grouped in a separate clade with other large-bodied acoels. Despite such conflicts, the branching pattern in the gene tree is well supported by morphological characters of sperm and body-wall musculature.

Letter to the Editor- Context Management Toolbox: A Linear Sequential Unmasking (LSU) Approach for Minimizing Cognitive Bias in Forensic Decision Making.

J Forensic Sci, July 2015, Vol. 60, No. 4 doi: 10.1111/1556-4029.12805 Available online at: onlinelibrary.wiley.com Letter to the Editor— Context Management Toolbox: A Linear Sequential Unmasking (LSU) Approach for Minimizing Cognitive Bias in Forensic Decision Making Sir, The 2009 NAS report (1) criticized forensic scientists for making insufficient efforts to reduce their vulnerability to cogni- tive and contextual bias. Over the past few years, however, the field has begun to take steps to address this issue. There have been major workshops on cognitive bias, and the Organization of Scientific Area Committees (OSAC), 1 as well as the National Commission on Forensic Science, have created committees on Human Factors that are specifically charged with examining this issue. 2 A number of tools and methods for minimizing bias are under consideration. Some of these tools have already been imple- mented in a few forensic laboratories. In general, these tools are designed to protect and enhance the independence of mind of forensic examiners, particularly those who rely on subjective judgment to make their decisions. Several types of contextual information are of concern, as illus- trated in Fig. 1. We organize them into a taxonomy of five levels (based on a four-level taxonomy suggested by Stoel et al. [2]). The five-level taxonomy differentiates task-irrelevant information that may be conveyed to an analyst by the trace evidence itself (Level 1), the reference samples (Level 2), the case information (Level 3), examiners’ base rate expectations that arise from their experience (e.g., when the examiner expects a particular result— Level 4), and organizational and cultural factors (Level 5). A variety of tools are available for addressing cognitive bias. Different tools are useful for managing exposure to each level of task-irrelevant information. For example, case managers (3,4) is a straightforward tool for dealing with bias from case informa- tion (Level 3). In general, these procedures are designed to pre- vent contextual bias by protecting the examiner from exposure to task-irrelevant information. However, it is important to note that some types of information, while potentially biasing, may also be task relevant (5). These types of biasing information are more difficult to deal with. For example, in some instances, evidence that analysts must examine to perform their duties may contain information that is potentially biasing. This can pertain to cases in which Level 1 information, the trace evidence being evaluated, contains contextual informa- tion (e.g., blood spatter patterns that contain information about the nature of the crime, or handwriting and voice samples in which the meaning of the words is potentially biasing). Reference samples are another example of relevant material that is also potentially biasing (Level 2). These samples are clearly relevant because the analyst must compare them to trace evidence samples to determine whether they are similar enough to conclude that they come from the same source. But it is pos- sible that an analyst’s interpretation of the trace evidence might inadvertently be influenced by knowing the characteristics of the See: http://www.nist.gov/forensics/osac/hfc.cfm. The authors of this letter are comprised primarily from members of the OSAC Human Factors Committee, the Human Factors Subcommittee of the National Commission on Forensic Science, and authors of the original Sequential Unmasking.

Identification of the subspecies of Oreochromis niloticus (Pisces: Cichlidae) using restriction endonuclease analysis of mitochondrial DNA

Abstract Restriction endonuclease analysis of mitochondrial DNA (mtDNA) was used to characterize differentiation among the seven described subspecies of Oreochromis niloticus from East Africa and Egypt. Mitochondrial DNAs of 14 populations were examined with 42 restriction endonucleases. Two subspecies of Oreochromis spilurus were also examined. Approximately 8% of the mitochondrial genome of O. niloticus (17 070 ± 40 base pairs) was assayed; 29 (70%) of the 42 restriction enzymes that were examined displayed restriction phenotypes that varied among the samples analyzed. Several endonucleases produced restriction phenotypes which were diagnostic for the described subspecies of O. niloticus, though a few samples did not agree with the conventional taxonomy of the group. Extensive differentiation of some populations suggests that additional taxonomic recognition is warranted. Because all subspecies of Oreochromis niloticus could be distinguished by their unique restriction enzyme profiles, analysis of mtDNA can be used to identify the origin of cultured stocks. This study provides the first molecular key for the objective identification of this taxon.

Descriptive Genetics of Cichlid Fishes

The evolutionary biology of cichlids is unusual principally because of the extensive adaptive radiations that have occurred in many endemic complexes (Futuyma, 1979). Within the major lakes of East Africa (Fryer and Iles, 1972) and smaller lacustrine systems in both Old and New Worlds (Taylor and Minckley, 1966; Trewavas et al., 1972; Barlow, 1976; Taylor and Miller, 1982), endemic species display dramatic morphological and ecological adaptations. Prodigious numbers of endemic species occur in Lake Malawi (N = 500+; McKaye and MacKenzie, 1982; McKaye, personal communication), Lake Tanganyika (N = 150+; Bailey and Stewart, 1977), and Lake Victoria (N = 300+; Van Oijen et al., 1981). The apparent youth of many species in some of these systems presents at least two fundamental evolutionary questions: first, what mechanisms control divergence in ecology and functional morphology? and second, how do new species arise? While substantial insights have been made in the areas of functional anatomy and ecology by Barel et al. (1977), Greenwood (1981), Liem (1980), McKaye (1980), and their coworkers, the basic questions of trophic divergence and speciation have remained controversial (Sage and Selander, 1975; McKaye, 1980; Kornfield et al.,1982; McKaye et al., 1983; Trewavas, 1982; Dominey, 1984; Greenwood, 1984).