Earthen Structures Built by Ilyoplax dentimerosa (Crustacea,Brachyura, Ocypodidae)

Under observation, the small ocypodid crab Ilyoplax dentimerosa was found to commonly build three types of earthen structures: a barricade near its neighbour's burrow, a fence at an intermediate position between the burrows of the builder and its neighbour, and a minishelter near the builder's burrow. The sex ratio of barricade builders was found to be close to 1:1, whereas most of the fence builders were found to be female. Crabs against which barricades and fences were built, were usually smaller than the builders. Both barricade builders and fence builders had, in most cases, minishelters at the side, facing the barricade or the fence. Removal and rebuilding experiments for barricades and fences demonstrated that both structures functioned to deter the approach of the builder's neighbour to the builder's activity site. Fences also had the effect of restraining the movement of the builder toward the fence site.     

Barricade building in Ilyoplax pusillus (De Haan) (Crustacea : Brachyura)

Ilyoplax pusillus (De Haan, 1835) was sometimes found to build an earthen structure, termed a barricade, close to its neighbour's burrow. Most barricaders were males > 6.4 mm in carapace width. Either males or females were barricaded and almost all of them were smaller than their barricaders. Burrow to burrow distance between a barricader and its barricaded neighbour ranged from 1.6 to 7.2 cm. The home range of a barricaded crab was biased toward the areas devoid of the barricade, i.e. to other directions than the barricader's burrow, in either the presence or absence of the barricader. When a barricade was removed, the crab freed from it extended its home range towards the barricader's burrow. If the crab freed from a barricade moved towards the barricader, the former was frequently repelled by the latter. These findings suggest that barricades function as an aid to territorial defence by deterring invasion by a neighbour.     

Are barricading and neighbor burrow-plugging by male crabs ofIlyoplax pusilla (Crustacea: Brachyura: Ocypodidae) related to feeding or mating?

Large males ofIlyoplax pusilla engage in 2 unique antineighbor behaviors, i.e., the building of a barricade of mud close to the neighbor's burrow, and plugging the entrance of the neighbor's burrow with mud. Correlation of these two behaviors to other behaviors was studied through field observations. Burrow-plugging was more frequent in May–June, when males waved actively, than in August, when waving was less frequent but foraging activity was higher. Frequency of daily burrow-plugging activity correlated well with that of waving, but not with that of foraging. These data suggest that burrowplugging is related to reproductive activities rather than feeding. The relationship of barricading to either waving or feeding was unclear.     

The phylogenetic position of the zokors (Myospalacinae) and comments on the families of muroids (Rodentia)

Recent molecular studies have concluded that the genus Myospalax evolved from within the rodent subfamily Cricetinae. This conclusion was tested using the complete sequences from the mitochondrial 12S rRNA and cytochrome b genes. Based on our analyses, Myospalax appears to be sister to a clade containing the subfamilies Spalacinae and Rhizomyinae, and all three of these lineages appear to be basal to the superfamily Muroidea. Based on the position of these three lineages, we suggest that they be placed in a distinct family, the Spalacidae, rather than subsumed as subfamilies in the family Muridae. Finally, our analyses suggest that the earlier placement of Myospalax as a member of the Cricetinae is the result of a single misidentified specimen, which was not a Myospalax.     

Use of barricades as foraging sites byIlyoplax pusillus (Crustacea brachyura: Ocypodidae)

Earthen barriers, termed “barricades”, are often built around burrow entrances by the crabIlyoplax pusillus as an aid to defence of territories. The present study demonstrated that barricades are also used as foraging sites by crabs other than the barricade builders. No significant differences in carbon, nitrogen and chlorophyll-a contents of dried surface sediments were determined between barricades and intact substratum, but barricades had a lower water content. Barricade-foraging is described in relation to the position, structure and nutritional content of barricades.     

Phylogenetic relationships among mytilidae (Bivalvia): 18S rRNA data suggest convergence in mytilid body plans

Nearly complete sequences were determined for small-subunit (18S) rRNA genes from seven species representative of four subfamilies of Mytilidae: Modiolus modiolus and M. auriculatus (Modiolinae); Lithophaga lithophaga and L. nigra (Lithophaginae); Musculus senhousie and M. discors (Crenellinae); and Hormomya domingensis (Mytilinae). Small-subunit rRNA gene sequences were also determined for Solemya reidi (Subclass Protobranchia), Mya arenaria (Subclass Heterodonta), and Elliptio complanata (Subclass Paleoheterodonta) as outgroup taxa. Phylogenetic analyses including these and other nearly complete bivalve small-subunit rRNA sequences demonstrate support for the monophyly of the family Mytilidae and the subfamilies Crenellinae and Lithophaginae. However, the subfamilies Mytilinae and Modiolinae appear polyphyletic. Likelihood, parsimony, and distance analyses support the placement of H. domingensis (Mytilinae) in a clade with G. demissa (Modiolinae). This clade is distinct from those containing other species traditionally assigned to these two subfamilies. Kishino-Hasegawa tests support these nontraditional relationships, suggesting that the mytiliform and/or modioliform body plans have evolved independently in at least two mytilid lineages.     

Molecular systematics of basal subfamilies of ants using 28S rRNA (Hymenoptera: Formicidae)

For many years, the ant subfamily Ponerinae was hypothesized to contain the basal (early branching) lineages of ants. Recently the Ponerinae were reclassified into six poneromorph subfamilies based on morphological analysis. We evaluate this new poneromorph classification using 1240 base pairs of DNA sequence data obtained from 28S rRNA gene sequences of 68 terminal taxa. The molecular tree supported the monophyly of the ant family Formicidae, with 100% parsimony bootstrap (PB) support and posterior probabilities (PP) of 1.00, with the ant subfamily Leptanillinae as a sister group to all other ants (PB=62, PP=93). However, our analyses strongly support the polyphyly of the Poneromorph subfamilies (sensu Bolton). The Ectatomminae and Heteroponerinae are more closely related to the Formicoid subfamilies than to the rest of the poneromophs (PB=96, PP=100). The Amblyoponinae (PB=52, PP=96), Paraponerinae (PB=100, PP=100), Ponerinae (PB<50, PP=71), and Proceratiinae (PB=98, PP=100) appear as distinct lineages at the base of the tree and are identified as a poneroid grade. Monophyletic origins for the poneroid subfamilies Amblyoponinae, Paraponerinae, Ponerinae and Proceratiinae are supported in our analysis. However, the genus Platythyrea forms a distinct sister group to the Ponerini within the Ponerinae. The Heteroponerinae, based on our sample of Heteroponera, are associated with the subfamily Ectatomminae (PB=98, PP=100). Furthermore, our data indicate the genus Probolomyrmex belongs to the Proceratiinae as suggested by recent morphological analysis (PB=98, PP=100).     

Molecular systematics of Eumolpinae and the relationships with Spilopyrinae (Coleoptera, Chrysomelidae)

The 3400 species of Eumolpinae constitute one of the largest subfamilies of leaf beetles (Chrysomelidae). Their systematics is still largely based on late 19th century monographs and remains highly unsatisfactory. Only recently, some plesiomorphic lineages have been split out as separate subfamilies, including the southern hemisphere Spilopyrinae and the ambiguously placed Synetinae. Here we provide insight into the internal systematics of the Eumolpinae based on molecular phylogenetic analyses of three ribosomal genes, including partial mitochondrial 16S and nuclear 28S and complete nuclear 18S rRNA gene sequences. Sixteen morphological characters considered important in the higher-level systematics of Eumolpinae were also included in a combined analysis with the molecular characters. All phylogenetic analyses were performed using parsimony by optimizing length variation directly on the tree, as implemented in the POY software. The data support the monophyly of the Spilopyrinae outside the clade including all sampled Eumolpinae, corroborating their treatment as a separate subfamily within the Chrysomelidae. The systematic placement of the Synetinae remains ambiguous but consistent with considering it a different subfamily as well, since the phylogenetic analyses using all the available evidence show the representative sequence of the subfamily also unrelated to the Eumolpinae. The Megascelini, traditionally considered a separate subfamily, falls within the Eumolpinae. Several recognized taxonomic groupings within Eumolpinae, including the tribes Adoxini or Typophorini, are not confirmed by molecular data; others like Eumolpini seem well supported. Among the morphological characters analyzed, the presence of a characteristic groove on the pygidium (a synapomorphy of the Eumolpini) and the shape of tarsal claws (simple, appendiculate or bifid) stand out as potentially useful characters for taxonomic classification in the Eumolpinae.     

Satellite-DNA diversification and the evolution of major lineages in Cardueae (Carduoideae Asteraceae)

In a previous work, we characterized the HinfI satellite DNA family in the subtribe Centaureinae (Cardueae) demonstrating that a “library” of eight HinfI subfamilies would exist in the common ancestor of all Centaureinae, which were differentially amplified in different lineages. Now, we extend our study by analyzing a total of 219 additional repeats from fifteen species belonging to Carlininae, Echinopsinae and Carduinae, and comparing them to those of Centaureinae. Most HinfI sequences belonged to the subfamily II, although a few sequences of other subfamilies were detected in some species. Additionally, a new subfamily characteristic of several Carduinae species was discovered. Although phylogenetic trees grouped sequences by subfamily affinity instead of species provenance, when comparing repeats of the same subfamily, the degree of divergence between any pair of sequences was related to the evolutionary distance between the species compared in most cases. Exceptions were in comparisons between sequences of some Centaureinae species, and between sequences of some Carduinae species and those of Centaureinae. Our results demonstrate that: (1) At least nine HinfI subfamilies would exist in the common ancestor of Cardueae, each one differentially amplified in different lineages; (2) After differential spreading, sequences of each subfamily evolved concertedly through molecular drive, resulting in the gradual divergence of repeats between different species; (3) The rate to which concerted evolution occurred was different between lineages according to the evolutionary history of each one.     

Phylogeny of harvestmen family Gonyleptidae inferred from a multilocus approach (Arachnida: Opiliones)

Gonyleptidae is the second most diverse harvestmen family and the most studied in terms of morphology, behaviour, and ecology. Despite this, few phylogenetic studies have focused on gonyleptids, and those are based on a very limited number of taxa. We addressed this gap by constructing a phylogenetic hypothesis of the family using 101 taxa from all 16 gonyleptid subfamilies and four mitochondrial and nuclear loci (COI, 28S rRNA, 12S rRNA, and 16S rRNA). These were analysed under parsimony and likelihood optimality criteria (and using direct optimization for the former). Relationships among Gonyleptoidea and within each subfamily of Gonyleptidae were largely congruent between parsimony and maximum‐likelihood approaches. Taxonomic actions from our phylogeny include the following: Tricommatidae, new status, is restored as a family; Metasarcidae, new status, is recognized as a family and considered sister to the Cosmetidae; and Cranainae and Manaosbiinae are suggested as members of Gonyleptidae, restoring Roewer's concept of the family. Within Gonyleptidae, the “K92” group—composed of Sodreaninae, Caelopyginae, Hernandariinae, Progonyleptoidellinae, and Gonyleptinae—forms a clade, although the latter two subfamilies are not monophyletic. The genus Parampheres is here transferred to Caelopyginae, and “Multumbo” dimorphicus to Gonyleptinae. Gonyleptidae is characterized by the presence of a ventral process on the penis glans and a bifid apophysis on the male coxa IV. The long‐legged Mitobatinae can be considered monophyletic only if some short‐legged pachylines are included, or if we assume that elongate legs arose twice independently (in the true mitobatine genera and in Longiperna). Pachylinae, the most diverse gonyleptid subfamily, represents several distinct lineages. We further conclude that the traditional use of a small set of morphological characters in the systematics of Gonyleptidae is unable to explain the complex evolution of the family.     

Phylogeny of the Sympetrinae (Odonata: Libellulidae): further evidence of the homoplasious nature of wing venation

Abstract.  Sympetrinae is the largest subfamily of the diverse dragonfly family Libellulidae. This subfamily, like most libellulid subfamilies, is defined currently by a few wing venation characters, none of which are synapomorphies for the taxon. In this study, we used DNA sequence data from the nuclear locus elongation factor-1α and the mitochondrial loci 16S and 12S rRNA, together with 38 wing venation characters, to test the monophyly of the Sympetrinae and several other libellulid subfamilies. No analysis recovered Sympetrinae as monophyletic, partly because of the position of Leucorrhinia (of the subfamily Leucorrhininae) as a strongly supported sister to Sympetrum (of Sympetrinae) in all analyses. The subfamilies Brachydiplactinae, Leucorrhininae, Trameinae and Trithemistinae were also found not to be monophyletic. Libellulinae was the only subfamily supported strongly as monophyletic. Consistency indices and retention indices of wing venation characters used to define various subfamilies were closer to zero than unity, showing that many of these characters were homoplasious, and therefore not useful for a classification scheme within Libellulidae.     

Modes of evolution in the protease and kringle domains of the plasminogen-prothrombin family

Phylogenetic analysis of protease domains of the vertebrate plasminogen-prothrombin family revealed two major subfamilies: (1) a subfamily containing macrophage-stimulating protein (MSP), hepatocyte growth factor (HGF), plasminogen, and apolipoprotein(a) (APOA); and (2) a subfamily containing prothrombin, HGF activator, and plasminogen activators. There was evidence that these two subfamilies diverged prior to the divergence of amphibians and amniotes. The phylogeny indicated a close relationship of APOA from the European hedgehog, rhesus monkey, and human with plasminogen. Phylogenetic analysis of repeated kringle domains supported the hypothesis that APOA evolved independently in hedgehog and primates through numerous duplications of different kringle domains of the ancestral plasminogen. Phylogenies of kringle domains revealed two modes of evolution: (1) a conservative mode, whereby duplication of kringle domains occurred prior to cladogenesis and the same kringle structure has been maintained in different lineages (exemplified by plasminogen and prothrombin); and (2) a concerted mode, whereby kringle domains have duplicated since cladogenesis and thus orthologous relationships do not exist between kringles of different lineages (exemplified by APOA).     

Light‐microscopic examinations of sperm in several lineages of Carabidae (Insecta: Coleoptera): Implications for the evolution of sperm conjugation

Sperm show marked morphological diversity, but the processes and mechanisms driving this diversity have not been fully elucidated. The beetle family Carabidae represents a potential model system for studying sperm trait evolution. In this study, sperm traits (mainly conjugation and sperm conjugate gross morphology) of 42 species from nine subfamilies of Carabidae were examined using light microscopy. Except in Harpalinae, the type of conjugation was shared by all members of a particular subfamily: in Carabinae, Elaphrinae, Patrobinae and Brachinae, sperm conjugates were observed in which variable numbers of sperm clumped together; in Nebriinae, Cicindelinae and Trechinae, sperm were not organized as conjugates but were present individually; and in Broscinae, both individual sperm and sperm conjugates were observed. In the remaining subfamily, Harpalinae, sperm conjugates were formed in most species, but a loss of conjugation was observed in some species. Mapping the observed sperm traits onto within‐family molecular phylogenetic trees suggested that sperm conjugation was ancestral, with loss of conjugation evolving in several lineages. In sperm conjugates, a short spermatostyle (the axis of sperm conjugates) was the ancestral state, while a long spermatostyle evolved in subsequent lineages. In the long spermatostyle trait, the flexible type without a conspicuous 3D structure was ancestral, while the type with a conspicuous 3D structure, such as the spiral structure, evolved in derived lineages.     

Modes of Evolution in the Protease and Kringle Domains of the Plasminogen–Prothrombin Family

Phylogenetic analysis of protease domains of the vertebrate plasminogen–prothrombin family revealed two major subfamilies: (1) a subfamily containing macrophage-stimulating protein (MSP), hepatocyte growth factor (HGF), plasminogen, and apolipoprotein(a) (APOA); and (2) a subfamily containing prothrombin, HGF activator, and plasminogen activators. There was evidence that these two subfamilies diverged prior to the divergence of amphibians and amniotes. The phylogeny indicated a close relationship of APOA from the European hedgehog, rhesus monkey, and human with plasminogen. Phylogenetic analysis of repeated kringle domains supported the hypothesis that APOA evolved independently in hedgehog and primates through numerous duplications of different kringle domains of the ancestral plasminogen. Phylogenies of kringle domains revealed two modes of evolution: (1) a conservative mode, whereby duplication of kringle domains occurred prior to cladogenesis and the same kringle structure has been maintained in different lineages (exemplified by plasminogen and prothrombin); and (2) a concerted mode, whereby kringle domains have duplicated since cladogenesis and thus orthologous relationships do not exist between kringles of different lineages (exemplified by APOA).     

Phylogeny of muroid rodents: relationships within and among major lineages as determined by IRBP gene sequences

The rodent family Muridae is the single most diverse family of mammals with over 1300 recognized species. We used DNA sequences from the first exon ( approximately 1200bp) of the IRBP gene to infer phylogenetic relationships within and among the major lineages of muroid rodents. We included sequences from every recognized muroid subfamily except Platacanthomyinae and from all genera within the endemic Malagasy subfamily Nesomyinae, all recognized tribes of Sigmodontinae, and a broad sample of genera in Murinae. Phylogenetic analysis of the IRBP data suggest that muroid rodents can be sorted into five major lineages: (1) a basal clade containing the fossorial rodents in the subfamilies Spalacinae, Myospalacinae, and Rhizomyinae, (2) a clade of African and Malagasy genera comprising the subfamilies Petromyscinae, Mystromyinae, Cricetomyinae, Nesomyinae, and core dendromurines, (3) a clade of Old World taxa belonging to Murinae, Otomyinae, Gerbillinae, Acomyinae, and Lophiomyinae, (4) a clade uniting the subfamilies Sigmodontinae, Arvicolinae, and Cricetinae, and (5) a unique lineage containing the monotypic Calomyscinae. Although relationships among the latter four clades cannot be resolved, several well-supported supergeneric groupings within each are identified. A preliminary examination of molar tooth morphology on the resulting phylogeny suggests the triserial murid molar pattern as conceived by evolved at least three times during the course of muroid evolution.     

Evolutionary history of Stratiomyidae (Insecta: Diptera): the molecular phylogeny of a diverse family of flies

Stratiomyidae is a cosmopolitan family of Brachycera (Diptera) that contains over 2800 species. This study focused on the relationships of members of the subfamily Clitellariinae, which has had a complicated taxonomic history. To investigate the monophyly of the Clitellariinae, the relationships of its genera, and the ages of Stratiomyidae lineages, representatives for all 12 subfamilies of Stratiomyidae, totaling 68 taxa, were included in a phylogenetic reconstruction. A Xylomyidae representative, Solva sp., was used as an outgroup. Sequences of EF-1alpha and 28S rRNA genes were analyzed under maximum parsimony with bootstrapping, and Bayesian methods to recover the best estimate of phylogeny. A chronogram with estimated dates for all nodes in the phylogeny was generated with the program, r8s, and divergence dates and confidence intervals were further explored with the program, multidivtime. All subfamilies of Stratiomyidae with more than one representative were found to be monophyletic, except for Stratiomyinae and Clitellariinae. Clitellariinae were distributed among five separate clades in the phylogeny, and Raphiocerinae were nested within Stratiomyinae. Dating analysis suggested an early Cretaceous origin for the common ancestor of extant Stratiomyidae, and a radiation of several major Stratiomyidae lineages in the Late Cretaceous.     

Molecular phylogeny, taxonomy, and evolution of nonmarine lineages within the American grapsoid crabs (Crustacea: brachyura)

Grapsoid crabs are best known from the marine intertidal and supratidal. However, some species also inhabit shallow subtidal and freshwater habitats. In the tropics and subtropics, their distribution even includes mountain streams and tree tops. At present, the Grapsoidea consists of the families Grapsidae, Gecarcinidae, and Mictyridae, the first being subdivided into four subfamilies (Grapsinae, Plagusiinae, Sesarminae, and Varuninae). To help resolve phylogenetic relationships among these highly adaptive crabs, portions of the mitochondrial genome corresponding to the 16S rRNA gene were sequenced for all grapsoid genera occurring in America. The resulting phylogeny confirms most of the present grapsid subfamilies but suggests reclassification of some of the genera and recognition of new taxonomic units. The two American gecarcinid genera might not represent a sister group to the Grapsidae but rather appear to have evolved within the latter. Colonization of inland habitats evolved in several lineages of the grapsoids, resulting in various forms of nonmarine life and different degrees of independence from the sea.     

Phylogeny of the Geometridae and the evolution of winter moths inferred from a simultaneous analysis of mitochondrial and nuclear genes

Geometridae is one of the most diverse families within the Lepidoptera, comprising nine subfamilies. Winter moths, which have a unique life history, are found in three subfamilies. To examine the phylogeny of the Geometridae at the subfamily level and determine the evolutionary history of winter moths, we constructed phylogenetic trees for all nine geometrid subfamilies using two mitochondrial and two nuclear gene sequences. Specimens of all subfamilies were sampled from Japan. Simultaneous analyses of the combined data from all genes revealed that the Geometridae comprised two major clades: one with subfamilies Larentiinae and Sterrhinae, and the other with the remaining seven subfamilies. The second clade included the largest subfamily, Ennominae, and the subfamily Archiearinae, which is traditionally considered to be an ancestral lineage of the Geometridae. The Larentiinae+Sterrhinae clade contained one winter moth lineage, and the second major clade consisted of three winter moth lineages, including Alsophilinae, which contains winter moths exclusively. Using a Bayesian inference of divergence times, we estimated that geometrids began to diverge 54 Mya (62-48 Mya), whereas winter moth lineages differentiated from non-winter moth lineages 34-12 Mya, during the global cooling events in the Oligocene and the early Miocene. The adaptation to cool climates may have been a preadaptation that facilitated the winter moth life cycle.     

EVOLUTIONARY PATTERNS OF ALTERED BEHAVIOR AND SUSCEPTIBILITY IN PARASITIZED HOSTS

Adaptation is the usual context for interpreting parasite-host interactions. For example, altered host behavior is often interpreted as a parasite adaptation, because in some cases it enhances parasite transmission. Resistance to parasites also has obvious adaptive value for hosts. However, it is difficult to evaluate the adaptive significance of host-parasite interactions without considering the historical context in which these traits have evolved and if they can be predicted by host (or parasite) phylogeny. We examined the influence of host phylogeny on patterns of altered behavior and resistance to parasitism in a cockroach-acanthocephalan system. A consensus cladogram for cockroach subfamilies was produced from the morphological data of McKittrick. We used this cladogram to predict patterns of altered host behavior in seven cockroach host species. Each species was experimentally infected with a single species of acanthocephalan, Moniliformis moniliformis, a parasite that is transmitted when cockroaches are eaten by rodent final hosts. Activity patterns, substrate choices, and responses to light were measured for control and infected animals. These data were recoded into a behavioral matrix of discrete characters. We determined the most parsimonious distribution of the behavioral characters on the tree obtained from McKittrick's data. We then measured the concordance between the behavioral data and the cockroach cladogram with the consistency index (CI). We compared the observed CI to the expected value based on a randomization of observed character states. For three different models of evolutionary character change, there was no evidence of strong concordance (significantly large CI) between altered host behavior and host relationships. Parsimony analysis of the interior nodes of the phylogenetic reconstruction suggested that unaltered behavior was the ancestral state for most host behaviors. We also compared host phylogeny to a data set on the susceptibility of 29 cockroach species to infection with M. moniliformis. At the species level, there was a significant concordance between susceptibility and host phylogeny. This pattern was consistent with the finding that susceptibility of species varied significantly among different subfamilies. However, at the subfamily level, susceptibility was not strongly concordant with phylogeny. We predict that, given enough time, resistance should be lost in subfamilies that are currently resistant to parasitism. In spite of the potential importance of phylogeny in the evolution of behavior and susceptibility, we found little evidence for phylogenetic effects in this system. We conclude that changes in the behavioral responses of hosts to parasites and, to a lesser extent, changes in susceptibility are more frequent than cockroach speciation events in different cockroach lineages. This finding strengthens the assertion that at least some of the altered behaviors are adaptive for host and/or parasite.     

BEHAVIORAL CONVERGENCE AND ADAPTIVE RADIATION: EFFECTS OF HABITAT USE ON TERRITORIAL BEHAVIOR IN ANOLIS LIZARDS

Most studies of adaptive radiations focus on morphological aspects of differentiation, yet behavior is also an important component of evolutionary diversification, often mediating the relationship between animal ecology and morphology. In species within radiations that are convergent in ecology and morphology, we then also expect convergence in behavior. Here, we examined 13 Anolis lizard species to determine whether territorial strategies have evolved convergently with morphology and habitat use. We evaluated two aspects of territoriality: behavioral defense of space via territorial displays, and territory overlap within and between sexes. Controlling for the phylogenetic relationships of the taxa in our study, we found that species similar in perch height and diameter convergently evolved patterns of territory overlap, whereas species similar in habitat visibility (the proportion of space that can be seen from a perch) convergently evolved display behavior. We also found that species with greater display time have more extensive male–male territory overlap. This study provides strong evidence for the role of habitat in the evolution of territoriality and suggests that the social structure of a species ultimately evolves in concert with habitat use and morphology.