Martyn Kennedy

Can ecological theory predict the distribution of foraging animals? : a critical analysis of experiments on the ideal free distribution

Opinions differ on the empirical success of the Ideal Free Distribution. The Ideal Free model predicts that the distribution of organisms between resource sites should match the distribution of resources. Many studies report support for this prediction. We review tests of this model utilising a method of analysis derived from the psychological principle called the matching law. Our reanalysis revealed that the distribution of organisms is consistently less extreme than the distribution of resources. This systematic deviation from the Ideal Free Distribution means organisms underuse richer sites and overuse poorer sites. We examine how deviations from the Ideal Free Distribution may arise as a consequence of discrimination constraints, competitive interactions, competitive asymmetries and travel between sites, and recommend ways in which the design of future tests of the Ideal Free Distribution may be improved.

SEABIRD SUPERTREES: COMBINING PARTIAL ESTIMATES OF PROCELLARIIFORM PHYLOGENY

Abstract The growing use of comparative methods to address evolutionary questions has generated an increased need for robust hypotheses of evolutionary relationships for a wide range of organisms. Where a phylogeny exists for a group, often more than one phylogeny will exist for that group, and it is uncommon that the same taxa are in each of the existing trees. The types of data used to generate evolutionary trees can also vary greatly, and thus combining data sets is often difficult or impossible. To address comparative questions for groups where multiple phylogenetic hypotheses already exist, we need to combine different hypotheses in a way that provides the best estimate of the phylogeny for that group. Here, we combine seven seabird phylogenies (based on behavioral, DNA–DNA hybridization, isozyme, life history, morphological, and sequence data) to generate a comprehensive supertree for the Procellariiformes using matrix representation with parsimony. This phylogeny contains 122 taxa and represents a conservative estimate of combined relationships presented in the original seven source trees. We compared the supertree with results of a combined sequence data supermatrix for 103 seabird taxa. Results of the two approaches are broadly concordant, but matrix representation with parsimony provides a more comprehensive and more conservative estimate of the phylogeny of the group because it is less influenced by the largest of the source studies (which uses a single, relatively quickly evolving gene). Genetic data sets that can be combined in a supermatrix approach are currently less likely to be available than phylogenies that can be combined using some form of supertree approach. Although there are limitations to both of those approaches, both would be simpler if all phylogenetic studies made both their data sets and trees they generate available through databases such as TREEBASE.

CLADOGENESIS AS THE RESULT OF LONG-DISTANCE RAFTING EVENTS IN SOUTH PACIFIC TOPSHELLS (GASTROPODA, TROCHIDAE)

Abstract We used DNA sequences of lecithotrophic monodontine topshells, belonging to the genera Diloma, Melagraphia, and Austrocochlea, to ascertain how this group became established over a large area of the South Pacific Ocean. The phylogeny of the topshells was estimated using portions of two mitochondrial genes (16S and cytochrome oxidase 1) and one nuclear gene (actin). A range of divergence rates was used to estimate the approximate timing of cladogenetic events within their phylogenetic tree. These estimates allow us to unambiguously reject vicariant explanations for several major divergence events and to infer several dispersal events across wide stretches of ocean. The first were two initial dispersal events from Australia (1) to an area between Samoa and Japan and (2) to New Zealand. Subsequently, at least one, and possibly two, recent eastward dispersals took place from New Zealand to Chile and the Juan Fernandez Islands, and one further dispersal occurred from somewhere in the tropical Pacific to Samoa. Moreover, owing to the short‐lived nature of the topshell larvae, transoceanic larval dispersal is unlikely. The apparent paradox of a short larval phase and broad geographic range suggests that dispersal most probably occurred by rafting of adults on a suitable platform such as macroalgae; indeed, naturally buoyant bull kelp is the natural habitat of the most geographically widespread species in this group. Our molecular phylogenies imply that, despite of being an unlikely event, adult rafting in ocean currents has occurred on several occasions throughout the evolutionary history of topshells, resulting in their wide present‐day distribution.

Multiple cophylogenetic analyses reveal frequent cospeciation between pelecaniform birds and Pectinopygus lice.

Lice in the genus Pectinopygus parasitize a single order of birds (Pelecaniformes). To examine the degree of congruence between the phylogenies of 17 Pectinopygus species and their pelecaniform hosts, sequences from mitochondrial 12S rRNA, 16S rRNA, COI, and nuclear wingless and EF1-alpha genes (2290 nucleotides) and from mitochondrial 12S rRNA, COI, and ATPases 8 and 6 genes (1755 nucleotides) were obtained for the lice and the birds, respectively. Louse data partitions were analyzed for evidence of incongruence and evidence of long-branch attraction prior to cophylogenetic analyses. Host-parasite coevolution was studied by different methods: TreeFitter, TreeMap, ParaFit, likelihood-ratio test, data-based parsimony method, and correlation of coalescence times. All methods agree that there has been extensive cospeciation in this host-parasite system, but the results are sensitive to the selection of different phylogenetic hypotheses and analytical methods for evaluating cospeciation. Perfect congruence between phylogenies is not found in this association, probably as a result of occasional host switching by the lice. Errors due to phylogenetic reconstruction methods, incorrect or incomplete taxon sampling, or to different loci undergoing different evolutionary histories cannot be rejected, thus emphasizing the need for improved cophylogenetic methodologies.

Psyllid communication: acoustic diversity, mate recognition and phylogenetic signal

Acoustic signals play an important role in mate selection and speciation in diverse groups of insects. We report reciprocal acoustic mate signalling, often as highly synchronised duetting, for several species of psyllid (Hemiptera:Psylloidea). We reveal that considerable acoustic diversity is present in Australian psyllids belonging to the family Triozidae. The acoustic signals are species and gender specific. Our acoustic analysis and observations suggest that acoustic signals are important in both species recognition and mate selection in psyllids. We found a significant level of phylogenetic signal in the acoustic data when we compared divergence in genetic data (obtained from mitochondrial DNA sequences of the small subunit rRNA) with divergence in acoustic signals in two groups of Australian psyllids. Phylogenetic reconstruction based on DNA sequence data supports the monophyly of the Eucalyptus-feeding genus Schedotrioza Tuthill & Taylor, 1955, whereas a diverse but little known group on Casuarinaceae hosts appears to be paraphyletic. These two psyllid groups also differ in amounts of geographical and ecological sympatry. We found a significant positive correlation between acoustic distance and genetic distance using pairwise comparisons for all taxa, but the trends within the two groups differ due to a negative association between acoustic and genetic divergence among the sympatric taxa. Phylogenetic information in acoustic data may be greatest in recently speciating and allopatric groups because of increased acoustic divergence in sympatric taxa and greater acoustic convergence in more distantly related species. Additional keywords: acoustic communication, Allocasuarina, Casuarinaceae, Eucalyptus, Psylloidea, speciation, substrate vibration, Triozidae.

Untangling Long Branches: Identifying Conflicting Phylogenetic Signals Using Spectral Analysis, Neighbor-Net, and Consensus Networks

Long-branch attraction is a well-known source of systematic error that can mislead phylogenetic methods; it is frequently invoked post hoc, upon recovering a different tree from the one expected based on prior evidence. We demonstrate that methods that do not force the data onto a single tree, such as spectral analysis, Neighbor-Net, and consensus networks, can be used to detect conflicting signals within the data, including those caused by long-branch attraction. We illustrate this approach using a set of taxa from three unambiguously monophyletic families within the Pelecaniformes: the darters, the cormorants and shags, and the gannets and boobies. These three families are universally acknowledged as forming a monophyletic group, but the relationship between the families remains contentious. Using sequence data from three mitochondrial genes (12S, ATPase 6, and ATPase 8) we demonstrate that the relationship between these three families is difficult to resolve because they are separated by a short internal branch and there are conflicting signals due to long-branch attraction, which are confounded with nonhomogeneous sequence evolution across the different genes. Spectral analysis, Neighbor-Net, and consensus networks reveal conflicting signals regarding the placement of one of the darters, with support found for darter monophyly, but also support for a conflicting grouping with the outgroup, pelicans. Furthermore, parsimony and maximum-likelihood analyses produced different trees, with one of the two most parsimonious trees not supporting the monophyly of the darters. Monte Carlo simulations, however, were not sensitive enough to reveal long-branch attraction unless the branches are longer than those actually observed. These results indicate that spectral analysis, Neighbor-Net, and consensus networks offer a powerful approach to detecting and understanding the source of conflicting signals within phylogenetic data.

Phylogeny of “Philoceanus complex” seabird lice (Phthiraptera: Ischnocera) inferred from mitochondrial DNA sequences

The Philoceanus complex is a large assemblage of lice that parasitise procellariiform seabirds (petrels, albatrosses, and their relatives). We obtained mitochondrial 12S rRNA and cytochrome oxidase I DNA sequences from 39 species from diverse hosts and localities. Resolution of deeper relationships between genera was limited, however there is evidence for two major clades, one hosted by albatrosses, the other by petrels. Based on our results, the genera hosted by albatrosses are excellent candidates for detailed analysis of cospeciation. Our results also suggest that a previous estimate of a 5-fold difference in the relative rate of sequence evolution in lice and their avian hosts is an artefact of limited taxonomic sampling.

Patch choice with competitive asymmetries and perceptual limits : the importance of history

Abstract A model of patch choice, in which individuals choose between two sites with different continuous input rates, is presented. Individuals differ in their competitive ability and may not perceive small resource differences between these patches. The model is historical, in that the individuals are added to the system sequentially, building up a complete system. Including this historical aspect leads to a different result from that derived using equilibrium-centred models. Monte Carlo simulations of the model show that (1) the historical development of a distribution of animals significantly affects its final form, and (2) an equilibrium distribution may not be reached until long after all individuals are present. When individuals have different competitive abilities, the ‘free’ assumption of the ideal free distribution (IFD) is violated, giving rise to a distribution we call the ideal competitive-differences distribution (ICDD). As has been previously noted, several different ICDD outcomes are possible in a given situation, but our historical perspective suggests that deviations from the habitat-matching prediction of the IFD (usually undermatchings) are much more likely than previously realized. A widely cited example of the ICDD, for instance, fails to give the IFD-mimicking habitat-matching distribution as its most likely outcome. Lastly, perceptual limits in conjunction with competitive differences result in mismatches with the ICDD. It is suggested, therefore, that experimental results are likely to undermatch resources compared with predictions from both the IFD and the ICDD.

PHYLOGENY, BIOGEOGRAPHY, AND TAXONOMY OF AUSTRALASIAN TEALS

Abstract The taxonomy of the Australasian teals has been particularly unstable. Australasian Grey Teal (Anas gracilis) and Chestnut Teal (A. castanea) are widely viewed as specifically distinct, but the taxonomy of the New Zealand teals remains unsettled. Because conservation status is affected by taxonomic rank, it is important to resolve the status of the rare subantarctic teals. To estimate phylogenetic relationships of teals, we sequenced three mitochondrial DNA genes (12S, and ATPase 6 and 8). The resultant phylogeny unequivocally groups the Chestnut Teal with the Grey Teal, rather than with the New Zealand teals as has traditionally been held (Fleming 1953). A greater level of sequence divergence occurred within the New Zealand teals than between the Grey and Chestnut teals. This diversity, together with morphological and behavioral differences, implies that the New Zealand teals should be accorded specific status as A. aucklandica, A. nesiotis, and A. chlorotis. Although it is most likely that the teal that colonized the Auckland Islands and Campbell Islands originated in New Zealand, our data do not allow us to determine whether the ancestors of the Campbell Island Teal came from mainland New Zealand or the Auckland Islands. This uncertainty arises because, as our data show, the colonization events were separated by a short period of time.

The immunogenicity of the acetylcholinesterases of the cattle lungworm Dictyocaulus viviparus

Somatic extracts and excretory/secretory (ES) products of the adult stage of the cattle nematode, Dictyocaulus viviparus, were examined for acetylcholinesterase (AChE) activity. Both were found to contain activity which had an optimum pH of 9.5, however, the adult ES products contained over 200 times more AChE activity per unit protein. Gel electrophoresis and specific enzyme staining revealed 5 migratory isoforms of AChE which were common to adult ES products and adult homogenates. Comparison of L3 with L4 and adult extracts indicated that the AChE were only produced by later developmental stages of this parasite. The antigenicity of D. viviparus AChE was demonstrated by binding to serum IgG from naturally and experimentally infected calves but the enzymes were not recognized by calves vaccinated twice with 400 Gy-irradiated larvae. This is the first report of helminth AChE release by a parasitic nematode in a pulmonary location. The presence of these enzymes in such high amounts in the ES products, along with their immunogenicity, suggests that they might have an important role to play in the immunobiology of D. viviparus in the lungs.