Abiotic determinants of the fynbos/succulent karoo boundary,South Africa

This study investigates the influence of texture, soil moisture and nutrient status on the growth and survival of seedlings of two typical fynbos (Leucadendron pubescens and Passerina vulgaris) and succulent karoo (Ruschia spp.) species, which grow in the boundary zone between these two vegetation types. Seedlings of each species were grown in shalederived and sandstone‐derived soils and under xeric and mesic regimes. Under the xeric regime, the shale‐derived and sandstone‐derived soils represented fine and coarse‐textured soils, respectively. Under the mesic regime, the same soils represented nutrient‐rich and nutrient‐poor soils, respectively. The seedlings of both fynbos species died rapidly under the xeric regime, irrespective of soil type. In contrast, the succulent karoo seedlings survived for over 77 days without water. Under mesic conditions, the fynbos seedlings grew faster than the succulent karoo seedlings, irrespective of soil type. Fynbos seedlings appear to be directly limited by the environment (moisture and salinity), whereas succulent karoo seedlings may be limited by interactions with other plants.     

Estimating average within-group relatedness from DNA fingerprints

We present a detailed analysis of a regression and an equivalent band-sharing technique for estimating mean within-group relatedness from DNA fingerprint data. First, we show that the relatedness estimate obtained from this technique tends to underestimate the pedigree relatedness in random-mating populations, but that the degree of underestimation will be small unless DNA fingerprint similarity among unrelated individuals is unusually high. We derive the exact asymptotic downward bias as a function of allele frequency and probabilities of identity by descent. We suggest some methods for removing the small downward bias in the regression estimate. Secondly, we show that the technique yields accurate estimates of parent-offspring, full, and half-sibling relatedness in natural populations of the red-winged blackbird Agelaius phoeniceus and indigo bunting Passerina cyanea.     

Brood parasitism by cowbirds: risks and effects on reproductive success and survival in indigo buntings

We observed brood parasitism by brown-beaded cowbirds (Molothrusater) on indigo buntings (Passerina cyanea) and estimated dieimpact of parasitism on the success of the individual buntingsin their current nests and in their future survival and reproduction.Rates of parasitism over 8 years were 26.6% in 1040 nests and19.8% in 693 nests in two areas in southern Michigan. Risk ofparasitism was high early in the season; half the bunting nestswere begun after the end of the cowbird season. Risk was independentof female age, plant containing the nest, or habitat The immediatecost of parasitism was 1.19 and 1.26 fewer buntings fledgedper nest. Bunting success was lower in parasitized nests withcowbird eggs (nests were more likely to be deserted or predated),lower when the cowbird nestling failed (nests were more likelyto be predated), and lower when the cowbird fledged (fewer buntingsfledged) compared to nonparasitized nests. Costs were due toremoval of a bunting egg when die cowbird laid its own egg andto competition for parental care of the cowbird and buntingnestlings. Buntings that fledged from nests where a cowbirdalso fledged were only 18% as likely to survive and return totheir natal area in the next year as buntings from nests wherea cowbird did not fledge. Long-term effects of cowbird parasitismon adult breeding later in the season, survival to the nextseason, and reproductive success in the next season were negligiblewhen compared between birds that reared a cowbird and birdsthat reared only a bunting brood, or between birds that wereparasitized and birds that escaped parasitism. The results indicatelittle long-term cost of brood parasitism on individual fitnessof adult buntings beyond the impact on the current nest andthe survival of buntings that fledge from it; nearly all costis to the parasitized brood.     

Gnidia (Thymelaeaceae) is not monophyletic: taxonomic implications for Thymelaeoideae and a partial new generic taxonomy for Gnidia

We address the generic limits of Gnidia (Thymelaeaceae) through a phylogenetic analysis of nuclear ribosomal DNA internal transcribed spacer (ITS) and plastid rbcL, trnL intron and trnL‐F intergenic spacer regions. Maximum parsimony and Bayesian inference were used to produce trees and assess internal support. The most significant conclusion drawn from the molecular analysis is that Gnidia is polyphyletic as currently circumscribed, comprising at least four distinct lineages that are each related to other genera within Thymelaeoideae. Gnidia pinifolia and G. racemosa are members of a clade within which Struthiola is embedded; a second group of species allies with Drapetes as sister to Passerina; and a third lineage corresponds to the previously recognized genus Lasiosiphon. The remaining species of Gnidia included in this study are allied with the Australian genus Pimelea. The taxonomic implications of these findings are discussed in relation to the principle of monophyly. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160 , 402–417.     

Effects of habitat edges and nest‐site characteristics on Painted Bunting nest success

Declines in populations of Painted Buntings (Passerina ciris) over the past several decades have led to their recent classification as a species of conservation concern. To better assess their status, we investigated factors associated with productivity and abundance of a population in south‐central Louisiana during 2010–2011. We monitored 41 Painted Bunting nests, 14 with video cameras, to identify predators, parasitism events, and improve nest success estimates. Vegetation measurements were also collected at nest sites and non‐nest sites to quantify habitat characteristics. We used an information‐theoretic approach to evaluate support for multiple models evaluating nest success. Highly supported models indicated large negative effects of Brown‐headed Cowbird (Molothrus ater) parasitism, and positive effects of increased canopy cover and distance to habitat edge on daily survival rates. Our estimate of daily survival rate was 0.94 ± 0.03 and the probability of survival was 0.25 ± 0.02. Point‐count data revealed that densities of Painted Buntings were greater in treeline habitats than in open scrub‐shrub and mature forest edge habitats. Furthermore, treelines had higher densities of large trees (>23 cm dbh) and percent canopy cover, variables positively associated with nest success, than open scrub‐shrub and forest edge habitats. In general, survival rates and causes of nest failure in southern Louisiana were similar to those determined for breeding populations of Painted Buntings at other sites. Our results suggest that treelines, despite having a high edge‐to‐area ratio, might be preferred nesting habitat for Painted Buntings in our study area.