PHYLOGENY OF THE NEMERTEAN SUBCLASS PALAEONEMERTEA (ANOPLA, NEMERTEA)

Abstract— A cladistic analysis based on 50 morphological characters was performed for 49 of the 98 species currently assigned to the subclass Palaeonemertea (phylum Nemertea), and six additional undescribed species. Thirty-five species were excluded from the parsimony analysis because of the high number of unknowns in the character matrix, and one species since it was considered a nomen nudum . An initial analysis suggested that the subclass Hoplonemertea is the sistergroup to the clade Palaeo- and Heteronemertea and the ingroup cladograms are rooted using a paraphyletic outgroup based on this information. Seventy-two equally most parsimonious cladograms were found; the consistency index was low but tree-length distribution for the character set is skewed to the left, and the cladograms are invariably shorter than trees based on random data. These cladograms suggested a character transformation series for the cerebral organ where this complex character reappeared several times after being absent. We considered this biologically implausible and the final discussion is based on three cladograms, one step longer than the most parsimonious, where the evolution of this character appears to be more realistic. The cladistic analysis indicates that many previously recognized genera (e.g. Cephalothrix, Procephalothrix and Cephalotrichella ), and higher taxa, are paraphyletic. It furthermore indicates that the previously suggested hypothesis of the Archinemertea as a monophyletic sistertaxon to Palaeonemertea is unsupported.     

Early stages and the classification of the milkweed butterflies (Lepidoptera: Danainae)

The Danainae, or milkweed butterflies, are a moderate-sized group of around 150 species that are of considerable ecological, physiological and behavioural interest. There are two currently accepted classifications for the subfamily and the aim of this study was to try to resolve this conflict using characters derived from the eggs, larvae and pupae. The 130 new characters (of which 85 are illustrated) are analysed by both phenetic methods (average linkage cluster analysis and principal coordinate analysis) and by cladistic techniques (Wagner tree, character compatibility analysis and manually derived cladograms). Overall, the results corroborate the more recent classification of the Danainae. However, some points of difference are found and, after component analysis, an alternative classification is presented in accordance with the conventions for constructing annotated Linnaean hierarchies.     

A method for estimating the relative importance of characters in cladistic analyses

The method of character importance ranking (CIR) is proposed here as a means for estimating the relative "importance" of characters in cladistic analyses, especially those based on morphological features. CIR uses the weighting variable to incrementally remove one character at a time from the analysis, and then evaluates the impact of the removal on the shape of the cladogram. The greater the impact, the more important the character. The CIR method for determining which characters drive the shape of a particular cladogram has several applications. It identifies the characters with the strongest (though not necessarily most accurate) signal in a cladistic analysis; it permits the informed prioritization of characters for further investigation via genetic, developmental, and functional approaches; and it highlights characters whose definition, scoring, independence, and variation should be reviewed with particular care. The application of CIR reveals that at least some cladograms depend entirely on a single character.     

Origins of New World monkeys

Fossil ceboid evidence is reviewed with reference to the origins and affinities of the New World monkeys. This evidence indicates that the ceboids evolved from a North American primate of omomyid-like form. The events of continental drift apparently had little to do with the origin and dispersion of the New World monkeys and direct relationships to the Old World monkeys are not indicated. Three of the five extant New World monkey subfamilies are represented in late Miocene deposits of South America and it appears that evolutionary events leading to extant Ceboidea occurred within the South American continent.     

Evaluating phylogenetic hypotheses of carpoids using stratigraphic congruence indices

Fossil carpoids possess a unique anatomy that is difficult to interpret; as a result, there are a number of competing phylogenetic hypotheses for carpoid taxa. Stratigraphic congruence indices provide a quantitative means of evaluating alternative cladograms where character coding is contentious; trees that show a statistically significant fit between stratigraphy and phylogeny are better supported by the fossil record. We here test the agreement between stratigraphic and cladistic data for 27 carpoid cladograms (24 have previously been published, three are novel). The results demonstrate that in analyses of subsets of carpoid taxa, the stratigraphic congruence of trees is not strongly affected by the interpretative model followed. However, when studying the relationships of carpoids with other deuterostomes, assuming that carpoids should be interpreted by reference to chordates/hemichordates (rather than echinoderms) leads to a poorer fit with the known stratigraphic ranges of taxa. Thus, the disputed calcichordate hypothesis (carpoids interpreted as stem and crown-group chordates and stem-group hemichordates) is much less congruent with stratigraphy than alternative models interpreting carpoids as stem or crown-group echinoderms.     

HISTORICAL BIOGEOGRAPHY OF THE HOLARCTIC: AREA RELATIONSHIPS, ANCESTRAL AREAS, AND DISPERSAL OF NON-MARINE ANIMALS

Abstract — Based on published phylogenies for 73 groups of Holarctic non-marine animals, interrelationships between the four Holarctic infraregions (western and eastern Nearctic, western and eastern Palearctic) are examined. The study includes analysis of resolved area cladograms, ancestral areas and dispersal indicated by cladistic subordinateness. Area relationships reflecting present continental configurations (Nearctic vs. Palearctic) dominate the material to the extent that one might speak of a general Holarctic area pattern. Paleocontinental (western Nearctic+eastern Palearctic, western Palearctic+eastern Nearctic) and disjunct patterns are relatively more frequent among groups of higher taxonomic rank. The western Nearctic seems to have played a bigger role than the other infraregions as a center of origin. Two computer programs for constructing resolved area cladograms, viz., COMPONENT 1.5 and COMPONENT 2.0, are compared. The three standard assumptions for biogeographical analysis are compared and arguments are presented in favour of Assumption 0.     

Analyse cladistique et Trilobites: un point de vue

On the basis of precise trilobite examples, the difficulties and interest in cladistic analysis are emphasized. The problem of distinguishing plesiomorphic and apomorphic characters is exemplified in Morgatia with reference to auxiliary impressions of the glabella and vincular furrows. In Crozonaspis , cladograms by themselves do not clarify the distinction of primitive versus derived features; the stratigraphical distribution of species, although not conclusive, is helpful in clarifying relationships. Although stratigraphical data are essential for reconstructing species lineages, they may be misleading when dealing with taxa above the species level. For all phylogenetical reconstructions, the completeness of the palaeontological and biogeographical record must be taken into consideration. D Trilobita, Phacopida, cladistics, Ordovician.     

Mapping cladograms into morphospaces

In cladistic analyses, taxa are grouped hierarchically into clades according to shared apomorphic character states to construct cladograms; cladograms are interpretable as phylogenetic hypotheses. In morphological space analyses, organism forms are represented as points in morphospaces; point proximities in morphospaces represent similarities that might be attributable to phenetic convergence and, consequently, may correspond inaccurately with hypothesized evolutionary relationships. A method for synthesizing phylogenetic results that are interpreted from cladistic analyses with phenetic results that are obtained from morphological space analyses is presented here; in particular, points that represent forms typifying taxa in morphospace are assigned as terminal nodes for appropriate cladograms that are mapped into morphospaces by positioning nonterminal nodes and orienting internodes according to a geometric algorithm. Nonterminal nodes may be interpreted as ancestors in phylogenetic hypotheses and occupy positions that represent particular organism forms in morphospaces. By mapping cladograms into morphospaces, therefore, evolutionary morphologists can reconstruct ancestral morphologies and test historical transformation hypotheses.     

Phylogenetic relationships and rates of evolution in primates: Allozymic data from catarrhine and platyrrhine species

The genetic electrophoretic variation at up to 43 protein loci was studied in four hominoid, three cercopithecoid, and three ceboid species. Phylogenetic reconstructions based on genetic distances show that the two chimpanzee species are closest to humans, while the gorilla diverged earlier than the split between humans and the chimpanzee. Within the cercopithecoids the green monkey apparently diverged earlier than the macaques, and within the ceboids, the owl monkey is only distantly related to the capuchin and squirrel monkeys. The hypothesis that rates of evolution at the level of protein electrophoretic variation are equal both among the groups, as well as within each group, could not be rejected.     

Problems with the use of cladistic analysis in palaeoanthropology

Cladistic analysis is a popular method for reconstructing evolutionary relationships on the human lineage. However, it has limitations and hidden assumptions that are often not considered by palaeoanthropologists. Some researchers who are opposed to its use regard cladistics as the preferred method for taxonomic «splitters» and claim it has lead to a revitalisation of typology. Typology remains a part of human evolutionary studies, regardless of the acceptance or use of cladistics. The assumption/preference for «splitting» over «lumping» in cladistics (alpha) taxonomy and the general failure to evaluate (post-hoc) such taxonomies have served to reinforce this assertion.

Researchers have also adopted a number of practices that are logically untenable or introduce considerable error. The evolutionary trend of human encephalisation, apparently isometric with body size, and concurrent reduction in the gut and masticatory apparatus, suggests continuous cladistic characters are biased by problems of body size.

The method suffers a logical weakness, or circularity, leading to bias when characters with multiple states are used. Coding of such characters can only be done using prior criteria, and this is usually done using an existing phylogenetic scheme. Another problem with coding character states is the handling of variation within species. While this form of variation is usually ignored by palaeoanthropologists, when characters are recognised as varying, their treatment as a separate state adds considerable error to cladograms.

The genetic proximity of humans, chimpanzees and gorillas has important implications for cladistic analyses. It is argued that chimpanzees and gorillas should be treated as ingroup taxa and an alternative outgroup such as orangutans should be used, or an (hypothetical) ancestral body plan developed. Making chimpanzees and gorillas ingroup taxa would considerably enhance the biological utility of anthropological cladograms.

All published human cladograms fail to meet standard quality criteria indicating that none of them may be considered reliable. The continuing uncertainty over the number and composition of fossil human species is the largest single source of error for cladistics and human phylogenetic reconstruction.     

A CLADISTIC ANALYSIS OF THE MICTINI (S. STR.) BASED ON ASIATIC TAXA (HETEROPTERA: COREIDAE)

Abstract  A cladistic analysis of the Asiatic genera of Mictini (s. str.) is made in the present paper. The results indicate that this group is monophyletic and their genitalia structrues are very similar, in spite of their variegated external forms. Derepterini Hsiao is proved to be a paraphyletic group and its synonymy with Mictini (s. str.) is supported by the cladograms. The cladograms show that there are some major differences between the mainly African Anoplocnemis and the other Asiatic genera.     

ON CONSENSUS, COLLAPSIBILITY, AND CLADE CONCORDANCE

Abstract — Consensus in cladistics is reviewed. Consensus trees, which summarize the agreement in grouping among a set of cladograms, are distinguished from compromise trees, which may contain groups that do not appear in all the cladograms being compared. Only a strict or Nelson tree is an actual consensus. This distinction has implications for the concept of support for cladograms: only those branches supported under all possible optimizations are unambiguously supported. We refer to such cladograms as strictly supported, in contrast to the semistrictly (ambiguously) supported cladograms output by various current microcomputer programs for cladistic analysis. Such semistrictly supported cladograms may be collapsed, however, by a variety of options in various programs. Consideration of collapsibility and optimization on multifurcations leads to some conclusions on the use of consensus. Consensus tree length provides information about character conflict that occurs between, not within, cladograms. We propose the clade concordance index, which employs the consensus tree length to measure inter-cladogram character conflict for all characters among a set of cladograms.     

分支系统学当前的理论和方法概述及华东地区山胡椒属十二个种的分支系统学研究

本文概述了当前分支系统学研究中涉及的主要理论和方法,包括性状的选取、性状状态和极性的确定、数据矩阵的分析计算、结果分支图的处理、分支图可靠性的评价及分支图的应用。本文同时以华东地区樟科山胡椒属Linderal2个种的分支系统学研究为例,讨论了用形态性状进行分支系统学研究中可能遇到的问题,也揭示了一些分支系统学与传统的系统学在应用性状推导进化关系上的不同点。对这12个种的分支系统学研究得出了一些不同于传统系统学方法所推测的山胡椒属内的系统发育关系,如分支系统学研究显示山胡椒组和球果组很近缘。在严格一致性分支图上,杯托组的黑壳楠和江浙山胡椒分别位于最原始和最进化的分支,表明这个组是复系类群。分支图也显示山胡椒组可能是复系类群。     

狭义巨缘蝽族支序分析研究——以亚洲材料为研究对象(异翅亚目:缘蝽科)(英语)

此文以狭义巨缘蝽族的亚洲各属为基础,对该族进行了支序分析,结果表明,尽管它们外形诸多变异,但其外生殖器结构甚为一致,此类群为一单系群无疑.文中支序图表明肖采瑜定的奇缘蝽族为一并系群,应为巨缘蝽族之次异名.支序图还说明主要分布于非洲的安缘蝽属与亚洲各属形态上有较大差异.     

Brain size affects female but not male survival under predation threat

There is remarkable diversity in brain size among vertebrates, but surprisingly little is known about how ecological species interactions impact the evolution of brain size. Using guppies, artificially selected for large and small brains, we determined how brain size affects survival under predation threat in a naturalistic environment. We cohoused mixed groups of small‐ and large‐brained individuals in six semi‐natural streams with their natural predator, the pike cichlid, and monitored survival in weekly censuses over 5 months. We found that large‐brained females had 13.5% higher survival compared to small‐brained females, whereas the brain size had no discernible effect on male survival. We suggest that large‐brained females have a cognitive advantage that allows them to better evade predation, whereas large‐brained males are more colourful, which may counteract any potential benefits of brain size. Our study provides the first experimental evidence that trophic interactions can affect the evolution of brain size.     

A cladistic analysis of the genus Lopezia (Onagraceae)

Lopezia, a genus of 22 species largely restricted to Mexico, forms a monophyletic group defined by the possession of two stamens in tetramerous flowerS. A cladistic analysis of the genus was performed using 16 characters from morphology, anatomy and embryology. Twenty of the 22 species were considered the terminal taxa. Polarity of the characters was based on the outgroup comparison method, using three alternative outgroups: the genus Fuchsia, Onagraceae excluding Ludwigia, and Epilobieae-Onagreae. Using Fuchsia as outgroup, 29 equally parsimonious cladograms were produced, each with 24 steps and a consistency index of 0.75. A successive weighting procedure was applied, resulting in 15 cladograms with consistency index of 0.85. The strict consensus cladogram defines eight monophyletic groups and supports most of the current sectional classification of Lopezia, with the exception that no synapomorphy defines section Jehlia. The larger sections Lopezia and Pelozia, although well-defined as clades, are not fully resolved internally. All cladograms support section Riesenbachia as monophyletic. The two alternative hypotheses for outgroups produced similar results: 61 most parsimonious trees, reduced after the successive weighting procedure to 15, which are identical to those produced with Fuchsia as outgroup. These results are discussed in the context of data on cytology and pollination biology.     

A Review of Current Theories and Methods in Cladistics and a Cladistic Study of Twelve Lindera Species in Eastern China

Cladistics has become a widely used method for phylogenetic reconstruction．Because of rapid improvement Of cladistic theories and methodologies,and application of new data,especially,molecular data,it is becoming realistic to reconstruct phylogenies of organisms,and to establish natural classifications based on these phylogenies．This paper reviews some current cladistic theories and methods in a practical way,such as choosing characters,defining character states,polarizing characters,analyzing data matrices, calculating consensus cladograms,choosing among multiple equally most parsimonious cladograms,estimating reliability of cladograms,and applying cladograms to classification, character evolution,and biogeography． Based on 36 morphological characters．a parsimony analysis of 12 species representing six sections in subgenus Lindera and an outgroup species from subgenus lteodaphne of the genus Lindera(Lauraceae)was conducted．The results suggest a close relationship between section Lindera and section Sphaerocarpae,which is different from the previous phylogenetic hypothesis within the genus．In the strict consensus cladogram,two species,L．megaphylla and L.chienii,from section Cupuliformes are in the most primitive and the most advanced clades respectively,indicating that the section is polyphyletic．The cladogram also suggests that section Lindera be a polyphyletic group．     

Revision of the genus Xylomoia Staudinger (Lepidoptera: Noctuidae), with descriptions of two new species

Seven species are included in the genus Xylomoia Staudinger, two of which are new: X. retinax sp.n. from the Novosibirsk area, Western Siberia, and from the Chelyabinsk area, southern Ural Mountains, and X. stangelmaieri sp.n. from Caorle, Venezia Giulia, on the Adriatic coast. A North American species, Chortodes didonea (Smith) comb.n., is removed from the genus. According to a cladistic analysis, the genus Xylomoia comprises one plesiomorphic species group, the chagnoni group, and two apomorphic groups: the graminea and strix groups. The latter are exclusively temperate Palaearctic. Xylomoia chagnoni (Barnes & McDunnough) is the only Nearctic species of the genus, and the loosely related X. apameaoides (Hacker) was recently described from Turkey. In geographical isolation, these two species have retained many ancestral features. In the more central area, the common ancestor of the graminea and strix groups has evolved into at least five species. The locality and rarity of the species of Xylomoia seemingly result from adaptation of the species to moist habitats, the larvae probably bore inside grass stems (the case of X. chagnoni ). What are called lock-and-key mechanisms may lead to the use of non-independent character states in a cladistic analysis; particularly in the case of homoplasy this kind of double-weighting may result in erroneous cladograms. In Xylomoia , deleting female lock-and-keys affected only the number of cladograms produced, whereas omitting the corresponding male characters had profound effects on the cladogram.     

HYBRIDS AND PHYLOGENETIC SYSTEMATICS II. THE IMPACT OF HYBRIDS ON CLADISTIC ANALYSIS

I examined three aspects of the cladistic treatment of a set of 17 F₁ hybrids of known parental origin: (1) impact of hybrids on consistency index (CI) and number of most parsimonious trees (Trees), (2) placement of hybrids in cladograms, and (3) impact of hybrids on hypotheses of relationship among species. The hybrids were added singly and in randomly selected sets of two to five to a data set composed of Central American species of Aphelandra (including the parents of all hybrids). Compared to analyses with the same number of OTUs all of which were species, the analyses with hybrids yielded results with significantly higher CI. There was no difference in Trees between analyses with hybrids versus species. There was thus no evidence that hybrids would appear to be more problematic for cladistic methods than species. Accordingly, hybrids will not be readily identifiable as taxa that cause marked change in these indices. About % of the hybrids were placed as the cladistically basal members of the lineage that included the most apomorphic parent. Relatively apomorphic hybrids were placed proximate to the most derived parent (ca. 13% of hybrids). Other placements occurred more rarely. The most frequent placements of hybrids thus did not distinguish them from normal intermediate or apomorphic taxa. When analyses with hybrids yielded multiple most parsimonious trees, these were no more different from each other than were the equally parsimonious trees that resulted from analyses with species. Most analyses with one or two hybrids resulted in minor or no change in topology. When hybrids caused topological change, they frequently caused rearrangements of weakly supported portions of the cladogram that did not include their parents. When they disrupted the cladistic placement of their parents, they often caused their parents to change positions, with at least one topology bringing the parental lineages into closer proximity with the hybrid placed between them. Hybrids between parents from the two main lineages of the group caused total cladistic restructuring. In fact, the degree of relationship between a hybrid's parents (measured by both cladistic and patristic distance) was strongly correlated with CI (negatively) and with the degree of disturbance to cladistic relationships (positively). Thus, hybrids between distantly related parents resulted in cladograms with low CI and major topological changes. This study suggests that hybrids are unlikely to cause breakdown of cladistic structure unless they are between distantly related parents. However, these results also indicate that cladistics may not be specially useful in distinguishing hybrids from normal taxa. The applicability of these results to other kinds of hybrids is examined and the likely cladistic treatment of hybrids using other sources of data is discussed.