Mixed species nesting associations in Darwin's tree finches: nesting pattern predicts predation outcome

Predation is the main cause of passerine nesting failure. Traditionally, large intraspecific group size is thought to accrue individuals with fitness benefits from increased predator vigilance and hence lower predation risk. To date, few studies have investigated interspecific group size in relation to predation risk. In the present study, we examined predation outcome in Darwin's small tree finch, Camarhynchus parvulus , in nests with many or few interspecific neighbours. We tested the predictions: (1) nests in mixed associations have lower predation than do more solitary nests; (2) mixed species nesting associations covary with nest site vegetation characteristics; (3) older (i.e. presumably experienced) males more commonly nest in mixed associations than younger males; (4) older males select more concealed nesting sites; and (5) controlling male age, females prefer to pair with males in mixed associations than at solitary nests. Almost half of all nests occurred in mixed associations (46%) compared to solitary nests (54%), and the overall distribution of nests was decidedly nonrandom, displaying a bimodal pattern. Nest site vegetation characteristics of the focal species were inconsistently associated with nesting pattern, but older males did select more concealed nesting sites. Controlling differences in surrounding vegetation characteristics, mixed nesting associations experienced markedly lower predation than solitary nests, and females showed a preference for males in mixed associations, as demonstrated by higher male pairing success.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 313–324.     

Effects of the introduced ectoparasite Philornis downsi on haemoglobin level and nestling survival in Darwin's Small Ground Finch (Geospiza fuliginosa)

Abstract: The physiological impacts and fitness costs of parasitism by an introduced ectoparasitic fly, Philornis downsi (Muscidae), were studied in nestlings of Darwin's Small Ground Finch, Geospiza fuliginosa (Geospizinae), on the Galápagos Archipelago. Whole blood haemoglobin (Hb) concentration was used to measure host response to ectoparasitism due to its high repeatability and validity, as well as for its key role in aerobic activities that affect fitness, such as flight capacity and nestling begging intensity. Increased numbers of ectoparasitic larvae of P. downsi were strongly correlated with lower Hb levels in nestlings in the absence of blood parasites. Furthermore, immature red blood cell counts were negatively correlated with Hb level and positively correlated with P. downsi intensity. Nestlings with high levels of parasitism suffered higher mortality, which varied with clutch size. Our results provide evidence that endemic Galápagos bird populations are physiologically compromised by P. downsi and experience substantial fitness costs due to ectoparasitism.     

Integrating fossils in a molecular-based phylogeny and testing them as calibration points for divergence time estimates in Menispermaceae

The phylogeny of extant Menispermaceae (Ranunculales) is reconstructed based on DNA sequences of two chloroplast genes (rbcL and atpB) from 94 species belonging to 56 genera. Fossilized endocarps represent 34 genera. The positions of these are inferred using 30 morphological characters and the molecular phylogeny as a backbone constraint. Nine of the thirteen nodes that are each dated by a fossil are used as calibration points for the estimates of molecular divergence times. BEAST is used to estimate stem a...     

Support for the nest mimicry hypothesis in Yellow-rumped Thornbills Acanthiza chrysorrhoa

The nest of the Yellow-rumped Thornbill Acanthiza chrysorrhoa (endemic to Australia) consists of a lower domed nest where the young are cared for and an upper cup-shaped structure, referred to as the false nest. Numerous hypotheses have been proposed to explain the primary function of the false nest, but their predictions remain largely untested. Here, we test predictions of the nest mimicry hypothesis (with artificial nests) whereby the empty false nest acts as a decoy, deflecting visual nest predators and/or brood parasites away from the true nest below, thereby increasing nesting success. Clear detection of the false nest by adversaries is an intrinsic aspect of nest mimicry; thus we also test whether conspicuous nests (natural) are favoured by natural selection. Specifically, (1) we compare predation level at artificial domed nests with and without a false nest; and (2) we analyse associations between nest site concealment and nesting outcome in natural nests in a wild population. Supporting the nest mimicry hypothesis, predation level was significantly lower for artificial domed nests with false nests, and for natural nests with lower levels of concealment.     

Karyological and taxonomic notes on Ophrys (Orchidoideae, Orchidaceae) from the Iberian Peninsula

Karyological information on Iberian Ophrys species is very limited. This paper provides the haploid and diploid chromosome numbers of 11 taxa of sect. Pseudophrys and sect. Ophrys , both of which are well represented in the Iberian Peninsula, and two taxa from Tunisia. The first data on chromosome numbers for O. vasconica (2 n  = 72, 74), O. ficalhoana (2 n  = 36), O. picta (2 n  = 36), O. sphegifera ( n  = 18, 2 n  = 36, 38) and O. passionis (2 n  = 36) are also presented, confirming the stability of the chromosome number in Ophrys . In addition, populations of the group O. omegaifera ( O. dyris and O. vasconica ), together with tetraploidy, pentaploidy and the existence of aneuploid phenomena, are reported for the first time in Iberia. The basic diploid number is always 2 n  = 36. The karyotypes of several species were analysed. Evolutionary trends in Ophrys chromosomes are discussed. Taxonomic and phytogeographical details are provided on several species or groups of species from Iberia.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003 , 142 , 395−406.