Myomorph Rodents Research Articles

Phylogeny and systematics of the endoparasitic astigmatid mites (Acari: Sarcoptiformes) of mammals: families Gastronyssidae, Lemurnyssidae, and Pneumocoptidae

We reconstruct the phylogenetic relationships of the mammal-associated endoparasitic mites belonging to 3 families, Gastronyssidae (42 species in 9 genera), Lemurnyssidae (4 species in 2 genera), and the monogeneric Pneumocoptidae (4 species) on the basis of maximum parsimony analysis of 120 morphological characters. In the strict consensus tree (all characters unordered and unweighted, Branch and Bound search option), these 3 families form a monophlyletic group with the first dichotomy between Pneumocoptidae-Lemurnyssidae and Gastronyssidae. The node joining these families is mainly supported by setal reductions. Such regressive characters alone provide relatively weak evidence for the monophyly of the group due to a greater probability of their homoplastic origin. On the other hand, the monophyly of each family is well supported by several progressive character changes. The family Gastronyssidae splits into 2 clusters. The first cluster represents the subfamily Yunkeracarinae and the second includes the subfamilies Gastronyssinae and Rodhoinyssinae. With respect to current classifications, there are 2 unexpected results in the tree: the position of the genus Gastronyssus Fain, 1955 (Gastronyssinae) within the core of the subfamily Rodhainyssinae and the polyphyly of the genus Opsonyssus Fain, 1959. The surprising placement of the genus Gastronyssus has the following explanation. In our data matrix, all distinctive derived character states characterizing this genus appear as autapomorphies and, therefore, do not affect the tree pattern. At the same time, these mites, being stomach parasites, exhibit the greatest degree of morphological reduction, including setae. Most of the character states shared with rodhainyssines are setal reductions and are of lesser reliability. The strict consensus of 14 trees obtained after successive weighting differs from the previous consensus tree mostly by the position of the genus Gastronyssus, which is the sister group to the all other rodhainyssine genera, excluding Phyllostomonyssus Fain, 1970. The genus Opsonyssus remained polyphyletic. We consider the 2 clusters observable in this tree as the subfamilies Yunkeracarinae (the genera Yunkeracarus Fain, 1957 and Sciuracarus Fain, 1964) and Gastronyssinae, respectively. The latter subfamily is divided onto 3 monophyletic lineages, which we rank as tribes: two monobasic tribes, Gastronyssini and Phyllostomonyssini tr. nov., and the tribe Rodhainyssini stat. nov., including the remaining genera, Eidolonyssus Fain, 1967, Mycteronyssus Fain, 1959, Opsonyssus, Rodhainyssus Fain, 1956, and the clade O. striatus Fain, 1967-O. phyllorhina Fain, 1959. A new genus Pseudoopsonyssus gen. nov. with species P. phyllorina (Fain, 1959) comb. nov. (type species), P. striatus (Fain, 1967) comb. nov., and P. zumpti (Fain, 1959) comb. nov. is established for this clade. The host-parasite associations of these endoparasitic mites are discussed, and a new hypothesis suggesting their secondary switching from the common ancestor of bats to myomorph rodents is proposed. Detailed taxonomic revisions of all 3 families based on examination of type materials are provided. Fifteen new species in 6 genera are described: Gastronyssus philippinensisBochkov et OConnor sp. nov., Rodhainyssus saccopteryx Bochkov et OConnor sp. nov., Opsonyssus pseudoindicus Bochkov et OConnor sp. nov., O. pteropodi Bochkov et OConnor sp. nov., O. klompeni Bochkov et OConnor sp. nov., O. macroglossus Bochkov et OConnor sp. nov., Mycteronyssus haplonycteri Bochkov et OConnor sp. nov., Eidolonyssus myersi Bochkov et OConnor sp. nov., Yunkeracarus apomys Bochkov et OConnor sp. nov., Y. rattus Bochkov et OConnor sp. nov., Y. limnomys Bochkov et OConnor sp. nov., Y. lophuromys Bochkov et OConnor sp. nov., Y. otomys Bochkov et OConnor sp. nov., Y. hylomyscus Bochkov et OConnor sp. nov., and Y. alticola Zabludovskaya sp. nov.

Colonic Separation Mechanism in Lagomorph and Rodent Species - a Comparison

Small herbivorous animals living on coarse food during cold or dry periods require a mechanism to be able to eat large quantities of food without losing the micro-organisms they need for fermentation. They use colonic separation mechanisms (CSM) that allow rapid transport of the less digestible food particles through the digestive tract whilst at the same time they retain micro-organisms and easily digestible food particles in their caecum for sufficiently long time periods in order for fermentation and microbial reproduction to take place. As a result of CSM. micro-organisms accumulate in the caecum. All species provided with a CSM utilise microbial proteins and vitamins via caecotrophy. A comparison is made between species belonging to the order Lagomorpha (hare, rabbit, pika) and species belonging to two suborders of Rodentia [myomorph rodents (rat, lemming, vole) and caviomorph rodents (guinea pig, chinchilla, nutria)]. The effects of the CSM are similar amongst the species studied, however, the efficiency of the CSM differs between individual species independent of the order/suborders to which they belong. The anatomy of the caecum and proximal colon is similar within the lagomorph order, but different compared to the rodents. It is more or less similar within each of the rodent suborders but differs between suborders. The mode of trapping and returning micro-organism is similar in myomorph and caviomorph rodents but different compared to the lagomorph species. Outside of the lagomorph and rodent orders CSM producing similar effects are found only in a few marsupial species. The anatomical and physiological background of the CSM in these species is not known.

The Middle Eocene North American Myomorph Rodent Elymys, Her Asian Sister Aksyiromys, and Other Eocene Myomorphs

Abstract The early Bridgerian (early middle Eocene) myomorph rodent Elymys complexus, from the Sheep Pass Formation near Ely, Nevada, is more variable in its dental morphology than originally described. Its similarity to Aksyiromys and other middle Eocene myomorphs from China and Central Asia suggests close relationships, which requires intercontinental interchange of these small rodents during the middle Eocene. At present, the biogeographic scenario for the origin and early evolution of Myomorpha that best fits the known record of occurrences is: evolution of Myomorpha from Sciuravidae in North America at least as early as the beginning of the middle Eocene, emigration of an Elymys-like myomorph from North America to Asia in the early middle Eocene, diversification of dipodoids and muroids in the later Eocene of Asia, emigration of Eucricetodon-like cricetids from Asia to North America (eumyine cricetids) in the latest Eocene, followed later by dipodids in the Miocene.

Small mammal inventory in the Shipstern Nature Reserve (Corozal District, Belize, Central America), a preliminary assessment

This small mammal inventory was conducted between May and September 2000 in the Shipstern Nature Reserve located at the northeastern limit of Belize in the Corozal District, Central America. In 11840 trap nights, 7 species of non-volant small mammals were captured, including 5 species of myomorph rodents and 2 species of didelphid marsupials. One species, Ototylomys phyllotis, accounted for 90.8% of the total captures, and may play a major role in the community structure of mammals in the reserve. The presence of Peromyscus yucatanicus in Shipstern Nature Reserve constitutes a first mention for Belize, and suggests that its range is extending more southerly to the limit agreed at present. Observations made on Sigmodon hispidus lead to formulate the hypothesis of a morphologically smaller population in the south of Quintana Roo, Mexico, and northern Belize, and further underlines the need for a complete revision of the genus in the Yucatan Peninsula. The sympatric diversity concretely obtained in Shipstern Nature Reserve is certainly underestimated, but nevertheless gives substance to the impression of a rodent community that is clearly affiliated to the partly endemic fauna of the Yucatan Peninsula, Mexico.

Evolutionary history of 4.5SI RNA and indication that it is functional.

To date, the small nuclear 4.5SI RNA has only been studied in the rat (Rattus norvegicus). Combining PCR and hybridization analyses, we have revealed 4.5SI RNA homologues sequences in the genomes of four myomorph rodent families (Muridae, Cricetidae, Spalicidae, and Rhizomyidae), and not in other myomorph families (Dipodidae, Zapodidae, Geomyidae, and Heteromyidae) or sciuromorph and caviomorph rodents. By Northern-hybridization, 4.5SI RNA has been detected in the common rat (R. norvegicus, Muridae), golden hamster (Mesocricetus auratus, Cricetidae), and Russian mole rat (Spalax microphthalmus, Spalacidae), but not in the related great jerboa (Allactaga jaculus, Dipodidae) or in four non-myomorph rodent species tested. cDNA derived from 4.5SI RNA of M. auratus and S. microphthalmus has been cloned and sequenced. The hamster RNA is found to differ from rat 4.5SI RNA by only one nucleotide substitution. For the mole rat, two variants of 4.5SI RNA are detected: short (S) and long (L) with length 101 and 108 nt, respectively. The L variant differs from the S variant as well as from murid and cricetid 4.5SI RNAs by both a 7 nt insertion and a varying number of nucleotide substitutions. The sequence similarity between the spalacid S-variant and murid/crecitid variants of 4.5SI RNA is 90%. Judging from species distribution, 4.5SI RNA genes emerged during the same period of time as the related short interspersed element B2 arose. This occurred after the divergence of Dipodidae lineage but before the branching of Spalicidae/Rhizomyidae lineage from a common myomorph rodent stem. S variant genes seemed to emerge in a common ancestor of spalacids and rhizomyds whereas L variant genes formed in spalacids following the divergence of these two families. The low rate of evolutionary changes of 4.5SI RNA, at least, in murids and cricetids (6 x 10(-4) substitutions per site per million years), suggests that this RNA is under selection constraint and have a function. This is a remarkable fact if the recent origin and narrow species distribution range of 4.5SI RNA genes is taken into account. Genes with narrow species distribution are proposed to be referred to as stenogenes.

Principles of rat subcortical forebrain organization: a study using histological techniques and multiple fluorescence labeling

In the present study, we introduce new views on neuro- and chemoarchitectonics of the rat forebrain subcortex deduced from traditional and current concepts of anatomical organization and from our own results. It is based on double and triple immunofluorescence of markers for transmitter-related enzymes, calcium-binding proteins, receptor proteins, myelin basic protein (MBP) and neuropeptides, and on histological cell/myelin stains. The main findings can be summarized as follows: (i) the dorsal striatum of rat and other myomorph rodents reveals a small caudate equivalent homotopic to the caudate nucleus (C) of other mammals, and a large putamen (Pu). (ii) Shell and core can be distinguished also in the ‘rostral pole’ of nucleus accumbens (ACC) with the calretinin/calbindin and neuropeptide Y (NPY) immunostaining. The shell reveals characteristics of a genuine striatal but not of an extended amygdala (EA) subunit. (iii) EA and lateral septum show striking similarities in structure and fiber connections and may therefore represent a separate parastriatal complex. (iv) The meandering dense layer (DL) of olfactory tubercle (OT) forms longitudinal gyrus- and sulcus-like structures converging in its rostral pole. (v) The core regions of the islands of Calleja that border the ventral pallidum (VP) sharing some of its features are invaded by myelinated fibers of the medial forebrain bundle (MFB). The island of Calleja magna is also apposed to an inconspicuous, slender dorsal appendage of VP. (vi) The VP is composed of a large dorsal reticulated part traversed by the myelinated GABAergic parvalbumin-immunoreactive axons of the MFB and a slender ventral non-reticulate part close to the islands of Calleja. (vii) Considering their close association to the limbic system, ventral striatum (VS) and VP may represent the oldest part of basal ganglia, whereas dorsal striatopallidal subunits were progressively developed in parallel to the growing neocortical influence on motor behavior.

Mus and Peromyscus chromosome homology established by FISH with three mouse paint probes.

Fluorescence-labeled DNA probes constructed from three whole house mouse (Mus domesticus) chromosomes were hybridized to metaphase spreads from deer mouse (Peromyscus maniculatus) to identify homologies between the species. Mus Chr 7 probe hybridized strongly to the ad-centromeric two-thirds of Peromyscus Chr 1q. Most of Mus 3 probe hybridized principally to two disjunct segments of Peromyscus Chr 3. Mus Chr 9 probe hybridized entirely to the whole Peromyscus Chr 7. Three Peromyscus linkage groups were assigned to chromosomes, based on linkage homology with Mus. The data also are useful in interpretation of chromosomal evolutionary history in myomorphic rodents.

A proposed path by which genes common to mammalian X and Y chromosomes evolve to become X inactivated.

Mammalian X and Y chromosomes evolved from an autosomal pair; the X retained and the Y gradually lost most ancestral genes. In females, one X chromosome is silenced by X inactivation, a process that is often assumed to have evolved on a broadly regional or chromosomal basis. Here we propose that genes or clusters common to both the X and Y chromosomes (X-Y genes) evolved independently along a multistep path, eventually acquiring dosage compensation on the X chromosome. Three genes studied here, and other extant genes, appear to be intermediates. ZFX, RPS4X and SMCX were monitored for X inactivation in diverse species by assaying CpG-island methylation, which mirrors X inactivation in many eutherians. ZFX evidently escaped X inactivation in proto-eutherians, which also possessed a very similar Y-linked gene; both characteristics were retained in most extant orders, but not in myomorph rodents. For RPS4X, escape from X inactivation seems unique to primates. SMCX escapes inactivation in primates and myomorphs but not in several other lineages. Thus, X inactivation can evolve independently for each of these genes. We propose that it is an adaptation to the decay of a homologous, Y-linked gene.

Relative brain size of some southern African myomorph rodents

Relative brain sizes, based on actual measurement of the brains of nine species of myomorph rodents, two insectivores and a macroscelidid are reported. Relative brain sizes of the macroscelidid and Tatera leucogasterwere far larger than those of the other rodents. With the exception of T. leucogaster, relative brain sizes were largest in semi-arboreal, omnivorous and nocturnal rodent species.

Scaling of the mandible in squirrels.

We compared the shape of the mandible among New World tree squirrels and selected outgroup taxa using linear measurements and areas defined by the median axis and conventional anatomical landmarks. We modified the median axis technique to define novel measurements, which proved complementary to those obtained from conventional landmarks. Allometric analyses showed that the scaling of the mandible among the New World tree squirrels is generally isometric (as has been observed in other groups of mammals), but diverges from isometry in a tendency in smaller animals for the masseteric ridge to be displaced anteriorly, the condylar process and posterior portion of the ascending ramus to be relatively elongated, and the coronoid process to be shortened. Allometric analyses also revealed the ways and extent that outgrowth taxa deviated from the scaling pattern observed for the New World tree squirrels. A flying squirrel (subfamily Pteromyinae), a moderate-sized callosciurine squirrel, and three species of pygmy tree squirrels from Asia and Africa show mandibular proportions very similar to those predicted for New World tree squirrels of corresponding size. Ground squirrels (tribe Marmotini) and successively more distant relatives such as Aplodontia, two myomorph rodents, and a rabbit show greater differences from the New World tree squirrels in their mandibular proportions. Combining the use of median-axis and conventional measurements makes it possible to examine changing relationships between locations of anatomically homologous landmarks and the geometry of the form.

Size-dependent morphology of the conductive bronchial tree in four species of myomorph rodents.

Size-dependent structural patterns in the conductive bronchial tree of four species of myomorph rodents of different body weight were determined by lung casts. The lungs of the harvest mouse, Micromys minutus, body weight 5-7 g, the house mouse, Mus musculus, body weight 35-45 g, the brown rat, Rattus norvegicus, body weight 200-400 g, and the African giant pouched rat, Cricetomys gambianus, body weight 1,200-1,800 g, were inflated to 20 cm H2O, frozen, freeze-dried, hardened, and filled with silicone rubber. The casts were pruned, and branching pattern, diameter, and volume of the conductive bronchial tree were determined using a binocular magnifier. All four species have four lobes on the right lung and an undivided left lung, and the central bronchial tree on either side shows an identical monopodial branching pattern. Although the ramification of the central conductive bronchi is not size-dependent, the diameter and volume are. The diameter of the left main bronchus equals 1.24% of body length in Micromys and 0.6% in Cricetomys, and the conductive bronchial tree makes up 13% of the total lung volume in Micromys and 6% in Cricetomys. Relatively wider airways and a decline in airway resistance with declining body mass in small mammals compared to large ones result in a high ventilatory dead space, which is compensated for by a higher breathing frequency.

Pyramidal cells ensheathed by perineuronal nets in human motor and somatosensory cortex.

This study presents data concerning the distribution of chondroitin sulphate proteoglycan-immunoreactive perineuronal nets in sensorimotor areas (Brodmann's areas 3, 1, 2 and 4) of the human cerebral cortex. In addition to previously described subpopulations of nonpyramidal neurons in neocortical areas, many large or medium-sized pyramidal cells in layers III and V, including Betz cells in the motor cortex, were shown to be net-associated and constitute about one-third of all net-associated cells. Such widespread occurrence of perineuronal nets around subpopulations of pyramidal cells is known from macaque monkeys but not from the cortex of myomorph rodents. Thus it appears that a certain proportion of net-associated pyramidal cells distinguishes individual cortical areas in highly evolved primates. This ratio may vary also with respect to species-dependent organization principles in nonprimate mammals.

The guinea-pig is not a rodent.

In 1991 Graur et al. raised the question of whether the guinea-pig, Cavia porcellus, is a rodent. They suggested that the guinea-pig and myomorph rodents diverged before the separation between myomorph rodents and a lineage leading to primates and artiodactyls. Several findings have since been reported, both for and against this phylogeny, thereby highlighting the issue of the validity of molecular analysis in mammalian phylogeny. Here we present findings based on the sequence of the complete mitochondrial genome of the guinea-pig, which strongly contradict rodent monophyly. The conclusions are based on cumulative evidence provided by orthologically inherited genes and the use of three different analytical methods, none of which joins the guinea-pig with myomorph rodents. In addition to the phylogenetic conclusions, we also draw attention to several factors that are important for the validity of phylogenetic analysis based on molecular data.

Sporadic amplification of ID elements in rodents.

ID sequences are members of a short interspersed element (SINE) repetitive DNA family within the rodent genome. The copy number of individual ID elements varies by up to three orders of magnitude between species. This amplification has been highly sporadic in the order Rodentia and does not follow any phylogenetic trend. Using library screening and dot-blot analysis, we estimate there are 25,000 copies of ID elements in the deer mouse, 1,500 copies in the gerbil (both cricetid rodents), and 60,000 copies of either ID or ID-like elements in a sciurid rodent (squirrel). By dot-blot analysis, we estimate there are 150,000, 4,000, 1,000, and 200 copies of ID elements in the rat, mouse, hamster, and guinea pig, respectively (which is consistent with previous reports) and 200 copies in the hystricognath rodent, nutria. Therefore, a rapid amplification took place not only after the divergence of rat and mouse but also following the deer mouse (Peromyscus) and hamster split, with no evidence of increased amplifications in hystricognath rodents. No notable variations of sequences from the BC1 genes of several myomorphic rodents were observed that would possibly explain the varied levels of ID amplification. We did observe subgenera and species-group-specific variation in the ID core sequence of the BC1 gene within the genus Peromyscus. Sequence analysis of cloned ID elements in Peromyscus show most ID elements in this genus arose prior to Peromyscus subgenus divergence. Correspondence of the consensus sequence of individual ID elements in gerbil and deer mouse further confirms BC1 as a master gene in ID amplification. Several possible mechanisms responsible for the quantitative variations are explored.

Photoperiod-induced changes in the proteins secreted by the male genital tract of the rodent Octodon degus.

The proteins secreted by the male genital tract were analyzed in the seasonally breeding rodent Octodon degus. The protein patterns from the fluids collected from sexually active animals were compared with those from animals in resting period, with others which were previously castrated, and with castrated animals which received testosterone replacement treatment. Fluids from cauda epididymides (CE), seminal vesicles (SV) and prostate glands (PG) were collected, and analyzed by polyacrylamide gel electrophoresis followed by different staining methods and densitometry. Modifications were detected in the protein patterns of resting or castrated animals. In CE fluid, the decrease of one protein band (45 Kda) and the uprising of another (210 Kda) were recognized after castration. In animals during resting period the changes were not as marked as in castrated animals. SV secretion demonstrated a similar response to resting phase and castration, because Protein SVS I (200 Kda) decreased or were not observed when these conditions occurred. PG fluid proteins were also modified after castration. In general, the more severe changes in the protein spectrum were induced by castration, despite radioimmunoassay showing that testosterone fall is even higher in resting period animals than in those castrated. Testosterone replacement resulted in recovery of a protein profile which is very similar to that of sexually active males. Results suggest that the androgenic control of male tract secretions would be rather different in this seasonal hystrichomorph when compared to the regulation system described for myomorph rodents.

Blood Supply to the Abdominal and Pelvic Regions in the Mediterranean Pine Vole, Microtus duodecimcostatus (Rodentia, Arvicolidae)

The abdominal and pelvic blood supply of the Mediterranean pine vole (Microtus duodecimcostatus) is described. A total of 13 individuals (seven males, six females) captured in the field (Sanaüja, Spain) were analysed by injection of coloured latex solution and subsequent dissection. The arrangements observed in all specimens show some common traits in relation to the patterns established in other Arvicolidae studied (Arvicola terrestris, Clethrionomys glareolus, Microtus H agrestis). These shared characteristics are centered on the origin of the deep circumflex iliac and the medial femoral circumflex arteries. As a particular variation from other Arvicolidae, some specimens of M. duodecimcostatus exhibit a gastrolienal trunk in the coeliac axis. Furthermore, the origin of the prostatic or the vaginal artery from the pudendoepigastric trunk observed in some specimens of M. duodecimcostatus has not previously been reported in other myomorph rodents.

Cloning and expression in insect cells of two pancreatic lipases and a procolipase from Myocastor coypus.

The physiological role of pancreatic lipases has traditionally been assigned solely to triacylglyceride metabolism, while the digestion of phospholipids requires the presence of the pancreatic phospholipase A2, a 14-kDa enzyme unrelated to pancreatic lipases. However, in the guinea pig, it was observed that the pancreatic phospholipase A2 was absent and that a guinea pig pancreatic-lipase-related protein 2 (GPL-RP2) was responsible for phospholipase activity, in contrast to the situation observed in other mammalian species. As the guinea pig is a member of the hystricomorph rodents, it was of interest to investigate if other species within this evolutionary suborder display similar characteristics. The coypu (Myocastor coypus) also a member of the hystricomorph rodents, was chosen for further investigations. The cDNAs encoding two pancreatic lipases and a procolipase from the coypu were cloned, expressed and characterized. One lipase, CoPL-RP2, was identified as belonging to the RP2 subfamily, while the second, CoPL, was found to belong to the classical pancreatic lipase subfamily. Enzymic characterization and sequence data suggest a role for coypu colipase as a specific cofactor for CoPL, while this coypu colipase cannot be an important cofactor for CoPL-RP2 in vivo. Also, the new lipase cDNA sequences were used in a phylogentic analysis to reinvestigate the taxonomical position of the hystricomorph rodents (e.g. coypu and guinea pig) with respect to the myomorph rodents (e.g. rat and mouse).

The arterial system of the abdominal viscera and the pelvis of the dormouse, Eliomys quercinus (Gliridae, Rodentia)

This paper deals with the origin, arrangement and variations of the abdominal and pelvic arteries in the garden dormouse, Eliomys quercinus. Fourteen latex-injected specimens (10 males, 4 females) were analysed by dissection. Measurements from the aortic bifurcation to the origin of the major arterial trunks were taken. The results obtained are compared with those reported for other myomorph rodents. The general arterial system of the dormouse basically agrees with the patterns observed in other rodent species. However, Eliomys quercinus shows some distinguishing features, such as the particular origin of the left and right gastric arteries, the distal arrangement of the deep circumflex iliac arteries, especially the right one, and the source of the medial femoral circumflex artery as a branch of the femoral artery.

Eutherian phylogeny from a primate perspective

Determinant formulas for up to 22 serum proteins from nineteen species in seven Eutherian orders (Chiroptera, Carnivora, Artiodactyla, Perrissodactyl, Rodentia, Proboscidea, Xenarthra) and Metatheria were derived by comparative determinant analysis from a primate (human) perspective. Plesiomorphic character states for taxon-pairs were inferred, including epitope patterns of the putative last common ancestor of Primates and non-primate Eutheria. Our approach, comparative determinant analysis, is exceptional among immunological methods in being able to define molecular character states for cladistic systematics. Average degrees of phylogenetic conservation of protein determinants varied between loci by 6.5-fold. Against the background of possible lineage-specific rates of molecular substitution, the clear immunological differentiation of the Asiatic elephant from (other) ungulates is discussed as to its phylogenetic relevance, as are the well-marked distances between guinea-pig and myomorph rodents, fissipeds and harbour seal, Mega- and Microchiroptera, or pig and ruminants. It is concluded that genetic drift influenced the rate of molecular evolution of mammalian orders to a different extent, e.g. more in the Proboscidean lineage than in the clade leading to the horse. It is concluded that the substitution rate of antigenic determinants of serum proteins correlates positively with speciation frequency in a phyletic lineage.

Eutherian phylogeny from a primate perspective

Determinant formulas for up to 22 serum proteins from nineteen species in seven Eutherian orders (Chiroptera, Carnivora, Artiodactyla, Perrissodactyl, Rodentia, Proboscidea, Xenarthra) and Metatheria were derived by comparative determinant analysis from a primate (human) perspective. Plesiomorphic character states for taxon-pairs were inferred, including epitope patterns of the putative last common ancestor of Primates and non-primate Eutheria. Our approach, comparative determinant analysis, is exceptional among immunological methods in being able to define molecular character states for cladistic systematics. Average degrees of phylogenetic conservation of protein determinants varied between loci by 6.5-fold. Against the background of possible lineage-specific rates of molecular substitution, the clear immunological differentiation of the Asiatic elephant from (other) ungulates is discussed as to its phylogenetic relevance, as are the well-marked distances between guinea-pig and myomorph rodents, fissipeds and harbour seal, Mega- and Microchiroptera, or pig and ruminants. It is concluded that genetic drift influenced the rate of molecular evolution of mammalian orders to a different extent, e.g. more in the Proboscidean lineage than in the clade leading to the horse. It is concluded that the substitution rate of antigenic determinants of serum proteins correlates positively with speciation frequency in a phyletic lineage.