Xenophilic mating preferences among populations of the jumping spider Habronattus pugillis Griswold

Sexual selection is thought to have driven the diversificationof courtship behavior and associated ornamentation between geographicallyisolated populations of the jumping spider Habronattus pugillisGriswold. In an attempt to understand the pathways of sexualselection during this diversification, we conducted reciprocalmating trials between two populations of H. pugillis (SantaRita [SR] and Atascosa [AT]) that differ in both male courtshipdisplay and secondary sexual ornamentation. Observations ofmating frequencies show a xenophilic mating preference in whichSR females have a stronger response to AT males than to SR males,while AT females show no difference in mating frequency. Theseresults are not consistent with a coevolutionary process inwhich male traits and female preferences evolve in concert,positively reinforcing each other. We discuss alternative pathwaysof sexual selection that may have acted in this system, includingthe possibility that female preferences and male traits haveevolved antagonistically. In addition, we found that SR femalesspent a higher proportion of time prior to copulation visuallyattentive to AT males versus SR males. This difference in visualattention prior to copulation was not seen in AT females andmay provide insights into our observations of xenophilic matingpreference.     

Phylogeny of Habronattus jumping spiders (Araneae: Salticidae), with consideration of genital and courtship evolution

Abstract. DNA sequences from the mitochondrial (including ND1, 16S) and nuclear (EF‐1α) genomes of about ninety‐four species were obtained to reconstruct phylogenetic relationships of Habronattus jumping spiders. Maximum parsimony trees were sought with both separate (mitochondrial, nuclear) and combined analyses; maximum likelihood trees were sought with both separate (ND1, 16S, EF‐1α introns, EF‐1α exons) and combined (mitochondrial, nuclear) analyses. All analyses agreed on some fundamental aspects of the tree, including the monophyly of the previously recognized agilis, amicus, dorotheae and americanus species groups. The deep phylogenetic structure is well resolved, placing the agilis, amicus, tranquillus and dorotheae groups basally. Several other previously unrecognized clades were well supported, including a newly formulated decorus group. The large group of species with modified male first and third legs was supported as monophyletic except for the surprising placement elsewhere of three species of the group. The phenotypic similarities between these three and the others are so detailed and precise that convergence in ornamentation can probably be ruled out. There are hints of phylogenetically distant genetic introgression involving the coecatus group. The combination Habronattus paratus is restored based on the species falling within Habronattus. Regarding patterns of character evolution, there was consistent support for the basal placement of several species groups with a long embolus, suggesting that there were more evolutionary reductions in embolus length than postulated in a previous morphological phylogeny. This is in accord with the expectation that there is a bias to an overly conservative interpretation of a character's evolution if it is interpreted on a phylogeny based in part on that same character. In contrast, the molecular phylogeny did not suggest any instances of the evolutionary transformation of one complex style of courtship into another, a possibility that could have been difficult to detect using the morphological phylogeny because of the same bias to conservativism.     

Prey classification by an araneophagic ant-like jumping spider (Araneae: Salticidae)

What to attack is one of the most basic decisions predators must make, and these decisions are reliant upon the predator's sensory and cognitive capacity. Active choice of spiders as preferred prey, or araneophagy, has evolved in several distantly related spider families, including jumping spiders (Salticidae), but has never been demonstrated in ant-like jumping spiders. We used prey-choice tests with motionless lures to investigate prey-choice behaviour in Myrmarachne melanotarsa , an East African ant-like salticid that normally lives in aggregations and often associates with other spider species. We show that M . melanotarsa chooses spiders as prey in preference to insects and, furthermore, discriminates between different types of spiders. Myrmarachne melanotarsa 's preferred prey were juvenile hersiliids and its second most preferred were other salticids. To date, all documented examples of araneophagic salticids have been from the basal subfamily Spartaeinae. Myrmarachne melanotarsa is the first non-spartaeine and also the first ant-like salticid for which araneophagy has been demonstrated.     

Optics of the ultraviolet reflecting scales of a jumping spider

The jumping spider Cosmophasis umbratica from Singapore is strongly sexually dimorphic. The males, but not the females, reflect ultraviolet as well as green-orange light. The scales responsible for this are composed of a chitin-air-chitin sandwich in which the chitin layers are three-quarters of a wavelength thick and the air gap a quarter wavelength (where lambda=600 nm, the peak wavelength of the principal reflection maximum). It is shown that this configuration produces a second reflectance peak at approximately 385 nm, accounting for the observed reflection in the ultraviolet. Other scales have a similar thickness of chitin but lack the air gap and thus produce a dull purple reflection. This novel mechanism provides the spiders with two colour signals, both of which are important in mating displays.     

Predator-prey interactions between web-invading jumping spiders and a web-building spider, Holocnemus pluchei (Araneae, Pholcidae)

Three species of web-invading salticid spiders, with different predatory strategies, were tested with Holocnemus pluchei in the laboratory: Portia fimbriata and Portia labiata , which practise aggressive mimicry, and Euyattus sp., which leaps from outside on to spiders in webs but does not practise aggressive mimicry. Portia was shown to be more efficient than Euryattus at catching H. pluchei. Portia fimbriata from Queensland was more consistent at using aggressive mimicry than was Portia labiata and was also more efficient at catching H. pluchei . The web-invaders that were more efficient at catching H. pluchei were also better able to avoid setting off bouncing, a special defence behaviour used by H. pluchei . An experiment, in which H. pluchei was artificially induced to bounce whenever the predator was near, provided additional evidence that bouncing is effective in defending H. pluchei against web-invaders.     

Effects of age and feeding history on structure-based UV ornaments of a jumping spider (Araneae: Salticidae)

Recent studies have shown for birds that females sometimes choose mates on the basis of condition-dependent variation in ultraviolet (UV, less than 400 nm) ornamentation, but there have been few comparable studies on invertebrates. Yet many invertebrates have UV structural coloration. Here, we investigate Cosmophasis umbratica, a jumping spider (Araneae: Salticidae) that has sexually dimorphic UV-iridescent ornamentation, and we provide evidence that male UV coloration is condition dependent in this species. Spectral-reflection patterns change with male age and prior feeding history. The position of the UV band (i.e. UV hue) of the carapaces of younger (field-collected as subadults and matured as adults in laboratory) males shifted, relative to older (field-collected as adults) males, significantly towards longer wavelengths. Food deprivation significantly decreased the spectral intensity of the abdomen, but not the carapace. Questions concerning the mechanisms by which UV ornaments change are highlighted, as are hypotheses concerning the role of condition-dependent UV variation in male-male competition and as a criterion used by females when making mate-choice decisions.     

Predatory and nesting behaviour of Cocalus gibbosus,a spartaeine jumping spider (Araneae: Salticidae) from Queensland

Abstract

Cocalus gibbosus was studied in the field in Queensland and in the laboratory. This is the first behavioural study of a species from the spartaeine genus Cocalus. C. gibbosus often omitted elements which are usually present in the predatory sequences of typical salticids and tended to lunge at prey from close range rather than leap from afar. Experiments showed that C. gibbosus prefers moths to other prey. In nature, C. gibbosus moulted and oviposited on silk sheets spun against tree trunks, and in the laboratory on sides of cages or blocks of wood, but this species never built an enclosing nest like typical salticids nor a large prey-catching web like some other spartaeines. C. gibbosus stalked across alien webs to catch spiders and insects, but it did not make vibratory signals. It did not stick to cribellate or ecribellate glue on alien webs. The behaviour of C. gibbosus is compared to that of other spartaeine salticids.     

Identification and characterization of a protostome homologue of peropsin from a jumping spider

Peropsin, a member of the opsin family, has characteristics of two functionally distinct opsin-groups, that is, amino acid residues conserved among opsins for light-sensing and a retinal-photoisomerase-like molecular property. Although such a bilateral feature of peropsin seems to be important for understanding the diversity of the opsin family, previous studies have been limited to higher deuterostome, vertebrate and amphioxus peropsins. Here, we report a protostome peropsin homologue from a jumping spider. We found a spider opsin that shares amino acid homology and conserved amino acid residues with known peropsins. The spider opsin-based pigment heterologously expressed in cultured cells exhibited photoisomerase-like isomerization characteristics and a bistable nature. Based on the characteristics of both the amino acid homology and its photochemical properties, we concluded that the spider opsin is the first protostome peropsin homologue. These results show that peropsin existed before the deuterostome–protostome split like other members of the opsin family. In addition, the spider peropsin was localized to non-visual cells in the retina, and fluorescence from reduced retinal chromophore was also observed in the region where peropsin was localized. These findings provide the first demonstration that the peropsin can form a photosensitive pigment in vivo and underlie non-visual function.     

Divergence in selection of host species and plant parts among populations of a phytophagous insect

The diversification of phytophagous insects is often attributed to diverging processes of host plant specialization onto different, often closely related, host plants. Some insect clades have diversified by specializing not only on different plant species but also on different plant parts of the same hosts. This is the case in Greya moths (Prodoxidae) where both Greya obscura and G. politella are tightly linked to host plants of the genus Lithophragma (Saxifragaceae). We assess how these species differ in their choice of plants and use of plant parts. Previous work showed that strong local host specialization in G. politella is mediated by floral scent variation among Lithophragma species. Here, we identify geographic variation in host plant use in the close relative G. obscura, relate the emerging patterns to previous studies of geographic variation in host use in G. politella and evaluate potential processes underlying the variation among and within species. First, we show that G. obscura also uses floral chemistry to locate hosts but that additional plant cues must be involved in deciding whether to oviposit on a plant, because females did not discriminate against chemically different host species in no-choice trials. We also found that, although all known populations of G. politella oviposit only in flowers, all G. obscura populations examined here distributed their eggs among both floral and scape tissues both in the field and in laboratory experiments. The distribution of eggs among plant parts, however, varied among moth populations, and also depended on the Lithophragma species they attacked. Together, these results show the potential for phytophagous insect species and populations to diverge in use of plant parts as part of the process of speciation and adaptation. These two layers of specialization enhance the potential for subsequent diversification in phytophagous insect lineages.     

Phylogenetic utility and evidence for multiple copies of elongation factor-1alpha in the spider genus Habronattus (Araneae: Salticidae)

In the continuing quest for informative genes for use in molecular systematics, the protein-coding gene Elongation factor-1alpha (EF-1alpha) has rapidly become one of the most prevalent "single-copy" nuclear genes utilized, particularly in arthropods. This paper explores the molecular evolutionary dynamics and phylogenetic utility of EF-1alpha in the salticid spider genus Habronattus. As has been reported for other arthropod lineages, our studies indicate that multiple (two) copies of EF-1alpha exist in Habronattus. These copies differ in intron structure and thus in size, making it possible to easily separate PCR amplification products. We present data for an intronless EF-1alpha copy for three Habronattus species. The presence of nonsense mutations and generally elevated rates of amino acid change suggest that this copy is evolving under relaxed functional constraints in Habronattus. A larger taxon sample (50 species plus outgroups) is presented for an EF-1alpha copy that includes both intron and exon regions. Characteristics of both regions suggest that this is a functional, orthologous copy in the species sampled. Maximum-likelihood relative-rate comparisons show that exon third codon sites are evolving more than 100 times as fast as second codon sites in these sequences and that intron sites are evolving about twice as fast as exon third sites. In combination, the EF-1alpha data provide robust, species-level phylogenetic signal that is largely congruent with morphologically well supported areas of Habronattus phylogeny. The recovery of some novel clades, and the unexpected fragmentation of others, suggests areas requiring further phylogenetic attention.     

Plant architectural traits influence residence time of a specialist jumping spider

The patch residence time of spiders has long been attributed to prey availability. We provide empirical evidence that plant architecture determines the residence time of a bromeliad-living spider. The residence time of spiders was longer on rosette-shaped plants. Males left their host plant faster than females, likely due to their mate-searching activity. We demonstrate that plant architectural traits mediate the patch-leaving tendency of specialist spiders.     

Hypersensitivity in the anterior median eye of a jumping spider.

Changes in sensitivity of the photoreceptor cells of the anterior median eye of the jumping spider Menemerus confusus Boes. et Str. have been studied by recording electroretinograms (ERGs) and receptor potentials. The amplitudes of the responses (ERGs and receptor potentials) increase during repetitive stimulation, with a maximum increase at 3-5 s intervals. The sensitivity of the photoreceptor cell is greater for about 60 s following illumination (maximum magnitude at 3-5 s) than it is during complete dark adaptation. This phenomenon, which we call 'hypersensitivity', is lost within one day following surgery in physiological saline. Upon loss of hypersensitivity, the sensitivity decrease during light adaptation is greater than for the normal eye and the small increase of sensitivity following the onset of illumination observed for the normal eye is lost.     

Divergence of mate recognition systems among conspecific populations of the plethodontid salamander Desmognathus santeetlah (Amphibia: Plethodontidae)

The disjunct geographic distribution of plethodontid salamanders of the genus Desmognathus provides excellent opportunities to test whether populations diverge in mate recognition systems so as to result in sexual incompatibility. Previous work has shown that sexual incompatibility may exist both among conspecific populations and between different species in this genus. Populations of the Santeetlah dusky salamander, Desmognathus santeetlah , are found at higher elevations in three mountain ranges in the southern Appalachian Mountains of eastern North America, where they are sympatric with congeneric species of similar body size. We report that statistically significant levels of sexual incompatibility exist among populations of D. santeetlah collected from across the species' range. Contrary to popular belief, but in accord with a growing body of empirical literature, aspects of mate recognition systems can diverge among conspecific populations of salamanders, resulting in incidental sexual incompatibility.     

XXXY sex chromosomes in males of the jumping spider genus Pellenes (Araneae: Salticidae)

Observations of male meiosis and female chromosome number indicate that eight species of Pellenes have the X₁X₂O male, X₁X₁X₂X₂ female sex chromosome system typical of salticids, four species have an X₁X₂X₃Y male, X₁X₁X₂X₃X₃X₃ female system, and one species has both X₁X₂O and X₁X₂X₃Y males. This is the first report of a Y chromosome in spiders. It is hypothesized that the X₁X₂X₂Y system was derived from an X₁X₂O system by a tandem X-autosome fusion which yielded the X₂ and a centric autosome-autosome fusion which yielded the Y. Data on heteropycnosis, chiasmata, segregation, chromosome number and arm length support this hypothesis. The distribution of the X₁X₂X₃Y system within the genus is phylogenetically confusing and suggests that the two sex chromosome systems have been maintained together as a polymorphism in some lineages for long periods of time or that there have been repeated derivations of the X₁X₂X₃Y or X₁X₂O systems.     

The biology of Tauala lepidus,a jumping spider (Araneae: Salticidae) from Queensland: display and predatory behaviour

Abstract

The display and predatory behaviour of Tauala lepidus Wanless, an abundant salticid in north Queensland rainforests, was investigated in the laboratory and, to a lesser extent, in nature. T. lepidus leapt and walked into alien webs to catch spiders and insects, and was captured and fed on by other spiders. Females ate each other’s eggs. During intraspecific interactions, a complex repertoire of displays was used. Courtship versatility occurred, each individual male having a conditional strategy of different behaviours depending on whether the female is at or away from her nest, and whether she is adult or subadult. Yet other combinations of displays occurred during male-male and female-female interactions. Apparently, pheromones on nests and draglines of females released male courtship. Abdomen twitching, a behaviour common to the display repertoires of many salticids, was an especially complex and pervasive behaviour of T. lepidus. T. lepidus also twitched its abdomen when it contacted alien webs and preyed on other species of spiders. The behaviour of T. lepidus is compared to that of Jacksonoides queenslandica Wanless, a species from the same group (Astieae).