Linking coevolutionary history to ecological process: doves and lice

Abstract Many host-specific parasites are restricted to a limited range of host species by ecological barriers that impede dispersal and successful establishment. In some cases, microevolutionary differentiation is apparent on top of host specificity, as evidenced by significant parasite population genetic structure among host populations. Ecological barriers responsible for specificity and genetic structure can, in principle, reinforce macroevolutionary processes that generate congruent host-parasite phylogenies. However, few studies have explored both the micro- and macroevolutionary ramifications of close association in a single host-parasite system. Here we compare the macroevolutionary histories of two genera of feather lice (Phthiraptera: Ischnocera) that both parasitize New World pigeons and doves (Aves: Columbiformes). Earlier work has shown that dove body lice (genus Physconelloides ) are more host specific and have greater population genetic structure than dove wing lice ( Columbicola ). We reconstructed phylogenies for representatives of the two genera of lice and their hosts, using nuclear and mitochondrial DNA sequences. The phylogenies were well resolved and generally well supported. We compared the phylogenies of body lice and wing lice to the host phylogeny using reconciliation analyses. We found that dove body lice show strong evidence of cospeciation whereas dove wing lice do not. Although the ecology of body and wing lice is very similar, differences in their dispersal ability may underlie these joint differences in host specificity, population genetic structure, and coevolutionary history.     

Bird Assemblage and Visitation Pattern at Fruiting Elmerrillia tsiampaca (Magnoliaceae) Trees in Papua New Guinea

Most tropical trees produce fleshy fruits that attract frugivores that disperse their seeds. Early demography and distribution for these tree species depend on the effects of frugivores and their behavior. Anthropogenic changes that affect frugivore communities could ultimately result in changes in tree distribution and population demography. We studied the frugivore assemblage at 38 fruiting Elmerrillia tsiampaca, a rain forest canopy tree species in Papua New Guinea. Elmerrillia tsiampaca is an important resource for frugivorous birds at our study site because it produces abundant lipid-rich fruits at a time of low fruit availability. We classified avian frugivores into functional disperser groups and quantified visitation rates and behavior at trees during 56 canopy and 35 ground observation periods. We tested predictions derived from other studies of plant–frugivore interactions with this little-studied frugivore assemblage in an undisturbed rain forest. Elmerrillia tsiampaca fruits were consumed by 26 bird species, but most seeds were removed by eight species. The most important visitors (Columbidae, Paradisaeidae and Rhyticeros plicatus) were of a larger size than predicted based on diaspore size. Columbidae efficiently exploited the structurally protected fruit, which was inconsistent with other studies in New Guinea where structurally protected fruits were predominantly consumed by Paradisaeidae. Birds vulnerable to predation foraged for short time periods, consistent with the hypothesis that predator avoidance enhances seed dispersal. We identified seven functional disperser groups, indicating there is little redundancy in disperser groups among the regular and frequent visitors to this tropical rain forest tree species.     

Relationship between song characters and morphology in New World pigeons

We studied the pattern of variation in song characters among 16 New World pigeon species belonging to different taxonomic groups defined by morphological characters. Structural, temporal and frequency characters of the song were analysed. Principal components analyses showed that species belonging to the same taxonomic group were also grouped together by their song characters. In addition, individuals were correctly assigned into taxonomic groups by discriminant function analyses in more than 87.8% of cases. These analyses also showed that more than 87.5% of the individuals could be correctly classified by species when all song characters were included. Correct classification of individuals by species and taxonomic groups dropped when character types were analysed separately, thus showing that structural, as well as temporal and frequency characters are fundamental to define species- and group-specific identities of New World pigeon's songs. Correspondence between patterns of vocal and morphological variation found in this study can be a consequence of evolutionary changes in morphology affecting song production, as for example body size changes that constrain the syrinx to produce certain acoustic frequencies.     

Using bioacoustic data to test species limits in an Indo‐Pacific island radiation of Macropygia cuckoo doves

The characterization of species limits and diversification patterns across the geographically complex Indo‐Pacific region has presented biogeographers and evolutionary biologists with great challenges. In the present study, we investigated the brown cuckoo dove (Macropygia amboinensis s.l.) species complex, whose distribution spans this entire region. We analyzed whether bioacoustic data are congruent with previous plumage‐based classifications and whether glacial land bridges have impacted bioacoustic diversification in these doves. Using an unusually large vocal dataset of > 300 recordings from over 30 islands and 24 taxa, we analyzed 29 bioacoustic frequency and temporal parameters and tested for a correlation between geographical and bioacoustic distances. We found a weak correlation between geographical and bioacoustic distances. We identified numerous lineages that are bioacoustically distinct and proposed their elevation to the species level, leading to a doubling of the number of species in this complex and indicating a high proportion of cryptic species‐level diversity that has previously gone unrecognized.     

Hybridization and postzygotic isolation patterns in pigeons and doves

Abstract.— The study of the patterns of reproductive isolation in relation to species divergence is critical for the understanding of the process of speciation. Comparative analyses of this kind were previously conducted in Drosophila , Lepidoptera, frogs, ducks, and birds in general. In the present study, we used information from the literature to analyze hybrid inviability in relation to species divergence in pigeons and doves. Four main patterns arose from this analysis: (1) as in the other groups studied, F₁ hybrid inviability gradually increases as species diverge, the time needed to reach total inviability being higher in birds than in the other groups; (2) as expected, the presence of geographic overlap does not influence the evolution of postzygotic isolation; (3) the percentage of unhatched eggs does not differ between hybrids of the first generation and the backcrosses, but it increases in the second hybrid generation; and (4) pigeons and doves follow Haldane's rule, as found in the other groups studied so far. The similarity between the results of this and previous studies contributes to the growing evidence suggesting that the patterns of the evolution of postzygotic isolation, and the process of speciation in general, are shared among animal groups.     

Diversity of feeding adaptations in certain columbid birds: A functional morphological approach

With gradual increasing complexity in higher vertebrate structure and function, the birds as a class have acquired very high degree of feeding adaptations for diverse food-niches. A comparative functional morphological study of the feeding apparatus of 6 species of columbid birds showing diversification in their food-habits reveals that some correlations exist between the form-function complexes of the feeding apparatus and the extent of diversity of food-habits shown by these birds. Among the species of columbid birds selected for the Study,Columba andStreptopelia are ground feeders and predominantly grain-eaters, although quite often they invade diversified food-niches.Treron andDucula, on the other hand, are almost exclusively fruit-eaters, plucking and swallowing fruits from the lofty tree branches, WhileColumba andStreptopelia show better kinesis of their jaws for ground-pecking,Treron. andDucula possess wider gape as well as stronger grasp of their bill for plucking off, grasping and swallowing large-sized fruits. Consequently, the size and pinnateness of the jaw muscles in these fruit-pigeons have developed far greater than those observed inColumba andStreptopelia. Further, inTreron andDucula, the thick and broad ‘venter externus’ slip of the M. pterygoideus ensures complete closure of the bill and possibly prevent any excess lateral expansion of the mandibular rami. Similar correlations have also been observed between the tongue features of columbid birds and the diversity of their feeding adaptation.     

To trill or not to trill? Territorial response to a heterospecific vocal trait in male collared doves, Streptopelia decaocto

Responding of individuals outside the conspecific range hasbeen largely explained by biases in sensory or cognitive systemstoward particular traits or trait values. More recently, ithas been shown that such responses might occur if individualsstill respond to signal traits that have been lost over time.However, empirical evidence remains scarce. We report a casesupporting the latter mechanism. Phylogenetic analysis suggeststhat the collared dove, Streptopelia decaocto, had lost thetrilled vocalization present in most congeneric taxa. We testedwhether males retained the ability to respond to these trillsin the context of territory defense. We synthesized trilledsongs by inserting trills from the sister species S. roseogriseainto S. decaocto songs. We show that trilled songs yielded higherresponses than did natural conspecific songs, and that the intensityof the response depended on the number of trilled elements.We also show that trilled songs elicited as strong reactionsas frequency modulated coos, which are stronger releasers ofterritorial response than are nonmodulated coos, but are notproduced by every males. Additional tests suggest that the frequencypattern is the most important feature of the trill used by males.However, it is still unknown whether reactions to trilled andfrequency modulated coos have the same perceptual basis. Toour knowledge, this study is the first report of a stronglydeviating signal that is still effective in vocal intrasexualcommunication in birds.     

Probability of Detecting Band-Tailed Pigeons During Call-Broadcast Versus Auditory Surveys

Abstract: Estimates of population trend for the interior subspecies of band-tailed pigeon (Patagioenas fasciata fasciata) are not available because no standardized survey method exists for monitoring the interior subspecies. We evaluated 2 potential band-tailed pigeon survey methods (auditory and call-broadcast surveys) from 2002 to 2004 in 5 mountain ranges in southern Arizona, USA, and in mixed-conifer forest throughout the state. Both auditory and call-broadcast surveys produced low numbers of cooing pigeons detected per survey route (x̄ ≤ 0.67) and had relatively high temporal variance in average number of cooing pigeons detected during replicate surveys (CV ≥ 161%). However, compared to auditory surveys, use of call-broadcast increased 1) the percentage of replicate surveys on which ≥1 cooing pigeon was detected by an average of 16%, and 2) the number of cooing pigeons detected per survey route by an average of 29%, with this difference being greatest during the first 45 minutes of the morning survey period. Moreover, probability of detecting a cooing pigeon was 27% greater during call-broadcast (0.80) versus auditory (0.63) surveys. We found that cooing pigeons were most common in mixed-conifer forest in southern Arizona and density of male pigeons in mixed-conifer forest throughout the state averaged 0.004 (SE = 0.001) pigeons/ha. Our results are the first to show that call-broadcast increases the probability of detecting band-tailed pigeons (or any species of Columbidae) during surveys. Call-broadcast surveys may provide a useful method for monitoring populations of the interior subspecies of band-tailed pigeon in areas where other survey methods are inappropriate.