The evolution of isolating mechanisms within a species population impedes gene flow. This allows isolated populations to diverge along different trajectories, which may ultimately lead to the formation of new species. Our attempts to understand the evolution of isolating barriers have benefited enormously from studies of divergent populations that are still recognized as members of the same species. The co-occurrence of five acoustically distinct populations of the bushcricket Mecopoda elongata in south India provided us with the opportunity to study one such divergence of sympatric populations of a single species. In sympatric populations that share identical ecology, sexual selection has the potential to play a prominent role in the maintenance of reproductive isolation. Based on a previous traditional morphometric study, Mecopoda elongata in India were thought to be a morphologically indistinguishable cryptic species complex. The lack of morphological divergence suggests a less significant role of ecology in the divergence of the group. One possibility is that songtypes may be maintained by the preference of Mecopoda elongate females for mating with a specific songtype. In this thesis I show that female phonotaxis to their ‘own’ call has the potential to contribute to behavioural isolation among the songtypes and in particular between two songtypes with overlapping temporal call parameters. This finding is supported by an independent no-choice mating experiment utilizing the same two songtypes. To investigate the cues other than song that Mecopoda elongata females’ may use to exercise preference for their own type, I examined the composition of cuticular lipids in the cuticle and the detailed structure of secondary sexual characters. I was able to differentiate all Mecopoda elongata songtypes with high probability based on CHC profiles and geometric morphometrics of the sub genital plate and cerci. My study reveals that divergence in sexual traits other than acoustic signals, although dramatically less obvious in nature, is present among Mecopoda elongata populations. This provides potential mechanisms for premating isolation among Mecopoda elongata songtypes in the wild suggesting that reproductive isolation is maintained by female preferences for male sexual signals. Additionally, I discovered a parasitoid Tachinid fly responsible for infecting three different songtypes of Mecopoda elongata, namely Double Chirper, Two Part and Helicopter. This Tachinid fly appears to have specialized hearing organ to track down calling Mecopoda elongata males throwing light on potential selection pressure and possible mechanism for Mecopoda elongata song divergence.

No description available.

Orientador: Diogo Cavalcanti Cabral-de-Mello / Resumo: Uma característica comum da evolução dos cromossomos sexuais é a acumulação de DNAs repetitivos, que estão envolvidos em sua diversificação e degeneração. Em gafanhotos o sistema ancestral dos cromossomos sexuais é o XO, mas em algumas espécies os cromossomos sexuais neo-XY surgiram por translocação Robertsonian entre o X ancestral e um par autossômico. Esse é o caso do Ronderosia bergii (Acrididae: Melanoplinae) que adicionalmente também apresentou uma grande inversão pericentrica no neo-Y, fazendo com que essa seja uma espécie singular para o entendimento da evolução dos cromossomos sexuais. Nesse estudo foi caracterizado os DNA satélites e Elementos de Transposição da espécie, com enfoque no entendimento das diferenças entre macho e fêmea e que estão putativamente associados aos cromossomos sexuais. Foi encontrado um total de 54 famílias de DNAs satélites e 56 famílias de TEs. Os DNAsat foram 13,5% mais abundantes no genoma do macho, enquanto os TEs foram apenas 1,02% mais abundantes no genoma da fêmea, evidenciando alta amplificação dos DNAsat no cromossomo neo-Y e menor envolvimento dos TEs na diferenciação dos cromossomos sexuais. A alta diferenciação entre os cromossomos sexuais é observada pela amplificação de múltiplos DNAsat no neo-Y com ocorrência de famílias exclusivamente mapeadas nesse cromossomo, entretanto, algum grau de homologia foi observado. Os dados do mapeamento dos DNAsat evidenciou um alto turnover dos neo-cromossomos sexuais em R.bergii em nível intra... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: A common characteristic along sex chromosome evolution is the accumulation of repetitive DNAs, which could account for their diversification and degeneration. In grasshoppers the ancestral sex chromosome system is XO, but in some species neo-XY sex chromosome emerged by Robertsonian translocation with an autosomal pair. This is the case of the Melanoplinae Ronderosia bergii that additionally present a large pericentric inversion in the neo-Y, making this a singular species to understand evolution of sex chromosomes. Here we characterized the satellite DNAs and Transposable Elements of the species focused in the understanding of differences between male and female genomes that are putatively associated with sex chromosomes. We found a total of 54 satDNA families and 56 families of TEs. The satDNAs were 13.5% more abundant in male genomes, while TEs were only about 1.02% more abundant in female genome, evidencing high amplification of satDNAs on neo-Y chromosome and minor role of TEs in sex chromosome differentiation. The high differentiation between the sex chromosomes is demonstrated by amplification of multiply satDNAs in neo-Y and occurrence of families exclusively mapped on this chromosome, although some degree of homology was noticed. Our data of chromosomal mapping of satDNAs evidenced high turnover of neo-sex chromosomes in R. bergii at intrapopulation level, caused by multiply paracentric inversions and other rearrangements like amplifications and transpositions. Final... (Complete abstract click electronic access below) / Mestre

Polyneoptera is an assemblage of eleven insect orders comprising the "orthopteroid" insects. It includes familiar insects such as grasshoppers, roaches, termites, earwigs and preying mantises; as well as the more obscure web-spinners, angel insects and ice-crawlers. We present a phylogenetic analysis of the polyneopteran orders based on 18S rDNA, 28S rDNA, Histone 3, and a coded morphology matrix for an extensive sampling of taxa. We investigate the use of congruence between separate datasets as an a priori measure of alignment quality. Our results support the paraphyly of Polyneoptera, the monophyly of Dictyoptera, sister taxon relationships between Embiidina + Phasmatodea and Dermaptera + Zoraptera, and a relatively basal placement of Plecoptera. The analyses also support a sister taxon relationship between the newly described Mantophasmatodea and Grylloblattodea, a small order of cryophilic insects confined to the northwestern Americas and northeastern Asia. This placement coupled with the morphological disparity of the two groups validates the creation of a new order for Mantophasmatodea. Our results also suggest the Direct Optimization (formerly Optimization Alignment) produces alignments that are more predictable across the parameter landscape than alignment via CLUSTAL X, as measured by congruence among independent data partitions. Dense taxon sampling and phylogenetic analysis of six molecular markers (12S, 16S, 18S, 28S, COII, and H3) and morphological data for the order Plecoptera demonstrates that the subordinal groups Arctoperlaria and Antarctoperlaria are monophyletic. Euholognatha and Systellognatha are also monophyletic, with the exception of the genus Megaleuctra which is the basal lineage for the order and deserves recognition as a distinct family (Megaleuctridae). Notonemouridae is strongly supported as a monophyletic clade. Within the Systellognatha Styloperlidae is the basal lineage, followed by Peltoperlidae then Pteronarcyidae, and Perloidea is a strongly supported monophyletic group with Chloroperlidae as sister taxon to Perlidae + Perlodidae. The family Gripopterygidae is strongly supported as paraphyletic. Many Plecoptera (stoneflies) exhibit a pre-mating communication known as "drumming." Species of the genus Isogenoides have complex drumming behavior in which (i) the male calls the female by tapping his abdomen against the substrate, (ii) the female answers with her own distinctive tapping, and (iii) the male responds with a confirmatory series of taps. These drumming patterns are specific to individual species and may vary within a species to form distinct dialects. Phylogenetic analysis for the genus based on six molecular markers (12S, 16S, 18S, 28S, COII, and H3) supports Yugus as its nearest extant relative and I. hansoni as the basal lineage within the genus. Drumming behavioral characters appear to be largely incongruent with the phylogeny.

No description available.

Darwinian sexual selection predicts that males with the most extravagant secondary sexual traits suffer elevated mortality. Although correlative evidence has generally not borne this idea out, recent research, including a field cricket study, showed that investment in sexually selected traits is costly to survival. I investigated male survival, ornamentation (song) and mating success in a North American grylline, Gryllus pennsylvanicus, to test the generality of previous work and highlight the importance of ecology differences to resource allocation. As the calling songs of older male G. pennsylvanicus are highly attractive to females, in Chapter 2 I tested whether male age correlated with calling song and found a weak but statistically significant correlation, thus leaving open the possibility that choosy females use an age-based indicator mechanism. In Chapter 3, I tested the condition dependence of male survival and calling effort. In contrast to previous work, I found that high condition males both called more and lived longer than low condition males, although there was no trade-off between survival and calling effort. The substantial condition dependence of calling effort suggests that calling effort is under strong directional selection. In Chapter 4 I tested whether female mating preferences resulted in strong selection on male calling effort. I also tested for the condition dependence of female mating preferences. I found that female choosiness was condition-dependent, but the rank of preferred male songs (preference function) was not. Both low and high condition females preferred high calling effort over low calling effort song. In Chapter 5 I tested for evidence of nonlinear selection on male survival that might explain the nonlinear pattern of male investment in survival seen in Chapter 3 (i.e. male survival leveled-off with increasing condition). I found that socially experienced females, but not virgin and naive females, exerted linear selection on male age. I discuss these and the other results of my thesis in the context of previous work on field crickets and condition-dependent ornamentation. Finally, Appendix A reports results that confirm ancient Chinese cultural knowledge that large headed male crickets are more successful in male-male combat.

Darwinian sexual selection predicts that males with the most extravagant secondary sexual traits suffer elevated mortality. Although correlative evidence has generally not borne this idea out, recent research, including a field cricket study, showed that investment in sexually selected traits is costly to survival. I investigated male survival, ornamentation (song) and mating success in a North American grylline, Gryllus pennsylvanicus, to test the generality of previous work and highlight the importance of ecology differences to resource allocation. As the calling songs of older male G. pennsylvanicus are highly attractive to females, in Chapter 2 I tested whether male age correlated with calling song and found a weak but statistically significant correlation, thus leaving open the possibility that choosy females use an age-based indicator mechanism. In Chapter 3, I tested the condition dependence of male survival and calling effort. In contrast to previous work, I found that high condition males both called more and lived longer than low condition males, although there was no trade-off between survival and calling effort. The substantial condition dependence of calling effort suggests that calling effort is under strong directional selection. In Chapter 4 I tested whether female mating preferences resulted in strong selection on male calling effort. I also tested for the condition dependence of female mating preferences. I found that female choosiness was condition-dependent, but the rank of preferred male songs (preference function) was not. Both low and high condition females preferred high calling effort over low calling effort song. In Chapter 5 I tested for evidence of nonlinear selection on male survival that might explain the nonlinear pattern of male investment in survival seen in Chapter 3 (i.e. male survival leveled-off with increasing condition). I found that socially experienced females, but not virgin and naive females, exerted linear selection on male age. I discuss these and the other results of my thesis in the context of previous work on field crickets and condition-dependent ornamentation. Finally, Appendix A reports results that confirm ancient Chinese cultural knowledge that large headed male crickets are more successful in male-male combat.

No description available.

Since several decades, field crickets of the subfamily Gryllinae under order Orthoptera have been used as a model group by researchers working in the field of neuroethology, behavioural ecology and bioacoustics. Subfamily Gryllinae is a much diversified group and members are diverse in their biological traits however the most commonly used model systems in the research fields belong to only three genera: Gryllus, Teleogryllus and Acheta. All the three genera are related to each other therefore, they fail to represent the wide diversity of ecological and behavioral traits that are encompassed by other members of Gryllinae. To understand the diversity in an evolutionary framework in field crickets, it is thus necessary to take into account the evolutionary background of the model systems. A phylogenetic analysis is a prerequisite for all evolutionary studies. A phylogeny hypothesizes the relationship among the studied taxa on the basis of homology drawn from all the characters that were used for the analysis. The phylogenetic tree is a branching diagram where related taxa are grouped together at nodes and the terminal ends of the branches are the studied taxa. The characters are mapped on to this tree thus indicating the hypothetical ancestral state of each character at the nodes and explaining the transformational stages of each character that gave rise to the current character state. This procedure helps in understanding the evolutionary history and understanding the patterns of relationships among taxa that in turn also help in identification of species. This process of identification and classification by phylogenetic reconstruction is formally known as “phylogenetic systematics”. The main goal of this thesis work was to understand the phylogenetic relationships among field crickets of the subfamily Gryllinae. This study is of importance in the field of orthopteran classification because since the 19th century, taxonomists proposed several taxonomic rankings and various classificatory schemes either by describing new classificatory levels or by upgrading existing taxonomic levels to higher levels. In addition, different sets of morphological characters have been used in proposing the classification hypotheses which in turn leads to the existence of several mutually exclusive hypotheses. Although there have been several changes in the taxonomic positioning of these crickets under Gryllinae, none so far have been based on a phylogenetic hypothesis. Therefore, I described 100 characters based on external and internal morphological structures of crickets belonging to 17 genera to test all the previously proposed classificatory hypotheses, provide a scheme for classifying these crickets under different hierarchical levels under Gryllinae and a strong base for conducting further evolutionary studies. The results lend full support to one of the previously proposed hypotheses for classification. Subfamily Gryllinae is a monophyletic clade where all the field crickets should be grouped under two tribes. The results also invalidate several tribes that have been erected in recent years. The second aim was to test species concepts by examining concordance in species boundaries generated from different data sets and to study the pattern of song evolution in field crickets. Therefore, for this study a field cricket belonging to genus Itaropsis was selected. Only one species of Itaropsis is known from the Indian subcontinent which was described from Sri Lanka. Interestingly, five call types of Itaropsis were encountered when a field survey was performed at four different localities in the Western Ghats of India. Males of the all five call types (varying from long trills to short chirps) looked morphologically very similar to each other. However, they differed in their calling song structure, I described four call features (carrier frqeuncy, syllable period, syllable duration and call duration) and classified the individuals into clusters by calculating distances using these call features. The clusters thus obtained were considered to reflect different species under the genus Itaropsis. To assure that the clusters thus obtained reflect different species, concordance between the results was tested by comparing these results with the clades of an available phylogeny for the collected individuals of this genus using both morphological and molecular data. The acoustic clusters showed concordance with the phylogenetic lineages largely however an absolute match was not found suggesting that these lineages cannot be called as distinct species. The pattern of evolution of songs in Itaropsis was examined by optimizing the call features on the phylogenetic tree derived from molecular data. This showed short chirps with a dominant frequency of 7 kHz to be the ancestral call type within this genus, from which long trills with long syllable durations have evolved. There were no significant patterns in the evolution of carrier frequency. In most crickets, the calling songs that are produced by males to attract their conspecific females are considered species specific therefore, the calling songs serve as an additional tool in identification of crickets. The third aim of my work was to use only call features of crickets in delineation of species but for higher number of species. Therefore, for this I used recorded calling songs of 14 species of field crickets and described their call features. I then used either five or seven call features to construct clusters based on Euclidean distances between the songs of all pairs of individuals. I also carried out a discriminant function analysis of these data to test the efficiency of species identification when taxa were specified a priori. I varied the number of species used for the analysis systematically from 5 to 14 to examine the effect of varying the number of taxa on correct species identification. The results showed that taxa number can be increased upto ten to obtain almost correct classification however, using six to seven taxa is optimal since they provide 90% accuracy in classification. To the best of my knowledge, this study on understanding the phylogenetic relationships among field crickets is the first to be carried out at subfamily level. Description of new call types reflecting multiple or incipient species under the genus Itaropsis and use of acoustic features in species identification of Indian field crickets is also a new contribution to the area of orthopteran systematics and phylogenetics.

Thesis (PhD)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Land use change is leading to rapid biodiversity loss in terrestrial ecosystems worldwide. Ecological networks (ENs) are systems of remnant natural habitat which remain intact in a transformed matrix, and have been suggested as a means to mitigate the effects of habitat loss and transformation and the resulting loss of biodiversity. Conceptually, ENs are similar to habitat corridors but are larger in scale and more heterogeneous in their design and management. Like corridors, the efficacy of ENs for biodiversity conservation has been called into question and requires empirical investigation. South Africa boasts a unique system of extensive ENs associated with exotic timber plantations, mostly within the highly endangered grassland biome and Indian Ocean Coastal Belt in KwaZulu-Natal Province, South Africa. In these regions, grasshoppers respond sensitively to management practices such as grazing, mowing and burning, justifying their a priori selection as an ecological indicator. In this study, I utilize grasshopper assemblages to determine the efficacy of ENs for biodiversity conservation and suggest guidelines for EN optimization. Specifically, I assess grasshopper assemblage sensitivity and robustness to habitat quality within ENs, congruence of grasshoppers with butterflies, and I identify indicator species which can be utilized by managers for EN assessment in future. I also perform a case study of isolated fragment utilization by a highly mobile generalist species, the bird locust, Ornithacris cyanea (Stoll, 1813) (Acrididae: Cyrtacanthacridinae). Grasshopper assemblages were sampled within ENs in two geographic regions (Zululand and the KwaZulu-Natal Midlands) and in two years (2007 and 2008) during the peak season of grasshopper abundance, late summer (February-April). Local-scale environmental variables relating to management practices and landscape-scale environmental variables relating to design of the ENs were quantified. Management practices explained, on average, two-thirds of the variability in grasshopper assemblages that could be explained, while design variables explained one-third. Grass height and the time since the last fire event were most consistently influential, while area, context, isolation, proportion of bare ground and proportion of forbs at a site, proved influential in some analyses but not others. This response was robust over time and among geographic regions. Grasshopper species richness and abundance were highly congruent with that of butterflies and did not differ among isolated fragments, connected corridors and reference sites, although they did differ among geographic regions. Not all grasshopper species responded similarly to ENs. There was a strong phylogenetic signal in species response to environmental variables, with the distribution of highly mobile families varying more among years. Linear, heavily disturbed power line servitudes had higher grasshopper abundance, and generalist species consistent with early successional assemblages. Reference sites had more graminivorous species and those with intermediate mobility. Three species of grasshopper were identified with IndVal and validated on an independently collected dataset as indicators of high habitat quality. A case study of the bird locust showed that populations of this highly mobile species were effectively isolated and undergoing anthrovicariance even at short distances. These results indicated that heterogeneous ENs supported diverse grasshopper assemblages, although movement among isolated fragments may have been limited. A grasshopper bioindication method for South Africa’s ENs is suggested and has great potential for assessment of a crucial and sensitive trophic layer within the ENs. This method should be field-tested and revised over time as grasshopper relative abundances and species compositions may change. Increased heterogeneity, simulation of multiple successional stages, and increased connectivity are expected to positively impact biodiversity, particularly of insect primary herbivores. Globally, ENs, if managed and designed appropriately, have potential to enhance biodiversity, particularly of smaller resident organisms which can utilize the ENs for movement and live within them. / AFRIKAANSE OPSOMMING: Veranderinge in grondgebruik lei tot ‘n vinnige verlies van biodiversiteit in terrestriële ekosysteme wêreldwyd. Ekologiese netwerke (ENs) is sisteme van oorblywende natuurlike habitat wat ongeskonde bly in getransformeerde matrikse, en is voorgestel as ‘n manier om die verlies aan biodiversiteit as gevolg van habitatverlies en transformasie te verminder. Konseptueel, is ENs soortgelyk aan habitat korridors, maar is groter in omvang en meer heterogeen in hulle ontwerp en bestuur. Soos korridors, is die effektiwiteit van ENs om biodiversiteit te bewaar bevraagteken, en vereis dit empiriese ondersoek. Suid-Afrika spog met ‘n unieke stelsel van uitgebreide ENs wat geassossieer is met uitheemse plantasies, meestal in die hoogs bedreigde grasveld bioom en Indiese Oseaan kusstrook in KwaZulu- Natal Provinsie, Suid Afrika. In hierdie streek reageer sprinkane sensitief op bestuurspraktyke soos beweiding, sny en brand. In hierdie studie het ek sprinkaan gemeenskappe gebruik om die effektiwiteit van ENs vir bewaring van biodiversiteit te bepaal en om riglyne te stel vir EN optimering. Spesifiek het ek sprinkaan gemeenskap sensitiwiteit en robustness tot habitat kwaliteit bepaal, oreenstemming tussen sprinkane en skoenlappers getoets, en het ek indikator species geïdentifiseer wat in die toekoms deur bestuurders gebruik kan word vir EN assessering. Ek het ook ‘n gevallestudie gedoen van geïsoleerde fragment benutting deur ‘n hoogs mobiele, algemene spesie, Ornithacris cyanea (Stoll, 1813) (Acrididae: Cyrtacanthacridinae). Sprinkaan gemeenskappe was versamel in twee geografiese gebiede (Zululand en die KwaZulu-Natal Midlands) en in twee jare (2007 en 2008) gedurende die seisoen van hoogste sprinkaan aktiwiteit, laat somer (Februarie – April). Plaaslike-skaal omgewingsveranderlikes met betrekking tot bestuurspraktyke en landskap-skaal omgewingsveranderlikes met betrekking tot die ontwerp van ENs is gekwantifiseer. Bestuurspraktyke verduidelik, gemiddeld, twee derdes van die variasie in die sprinkaan gemeenskappe, terwyl ontwerpveranderlikes een derde verduidelik. Grashoogte en tyd sedert die laaste brand was konsekwent invloedryk, terwyl area, konteks, isolasie, hoeveelheid kaal grond en hoeveelheid kruidagtige plantegroei invloedryk was in sekere analyses, maar in ander nie. Hierdie reaksie was konstant oor tyd en tussen geografiese gebiede. Sprinkaan spesies rykheid en hoeveelheid was hoogs kongruent met die van skoenlappers, en het nie verskil tussen geïsoleerde fragmente, verbinde korridors en verwysingsareas nie, maar hulle het verskil tussen geografiese streke. Nie alle sprinkaan spesies het soortgelyk gereageer tot ENs nie. Daar was ‘n sterk filogenetiese sein in spesies reaksies op die omgewingsveranderlikes, met meer variasie tussen jare in die verspeiding van hoogs mobiele families. Liniêre, hoogs versteurde kraglyn dienspaaie het hoer sprinkaan hoeveelhede gehad en algemene spesies wat geassosieer is met gemeenskappe in vroeë stadiums van suksessie. Verwysingsareas het meer graminivorous spesies gehad en spesies met intermediêre mobiliteit. Drie sprinkaan spesies is geïdentifiseer met IndVal en bevestig met ‘n onafhanklik versamelde dataset as indikators van hoë kwaliteit habitat. ‘n Gevallestudie op O. cyanea het aangedui dat populasies van hierdie hoogs mobiele spesie geïsoleerd is en dat hulle anthrovicariance ondergaan, selfs op kort afstande. Hierdie resultate dui aan dat heterogene ENs diverse sprinkaan gemeenskappe ondersteun, hoewel beweging tussen geïsoleerde fragmente dalk beperk is. Verhoogde heterogeneïteit, simulasie van verskeie suksessiewe fases en meer konnektiwiteit sal moontlik ‘n positiewe invloed op biodiversiteit hê, aangesien sprinkane verteenwoordigend was van insek primêre herbivore. Wêreldwyd, as ENs op ‘n gepaste manier bestuur en ontwerp word, het dit die potensiaal om biodiversiteit te bevorder. Dit is veral belangrik vir kleiner, plaaslike organisms wat ENs kan benut vir beweging en as leefhabitat. ‘n Sprinkaan bioindikasie metode vir Suid-Afrika se ENs is voorgestel en het groot potensiaal vir die assessering van ‘n belangrike en sensitiewe trofiese laag binne die ENs. Hierdie metode moet in die praktyk getoets word en hersien word oor tyd om veranderinge in sprinkaan relatiewe hoeveelhede en spesies komposisies in ag te neem.