Ground Tit Pseudopodoces Humilis Research Articles

Egg investment in response to helper presence in cooperatively breeding Tibetan ground tits

Life‐history theory predicts a trade‐off between current and future reproduction to maximize lifetime fitness. In cooperatively breeding species, where offspring care is shared between breeders and helpers, helper presence may influence the female breeders’ egg investment, and consequently, survival and future reproductive success. For example, female breeders may reduce egg investment in response to helper presence if this reduction is compensated by helpers during provisioning. Alternatively, female breeders may increase egg investment in response to helper presence if helpers allow the breeders to raise more or higher quality offspring successfully. In the facultatively cooperative‐breeding Tibetan ground tit Pseudopodoces humilis, previous studies found that helpers improve total nestling provisioning rates and fledgling recruitment, but have no apparent effects on the number and body mass of fledglings produced, while breeders with helpers show reduced provisioning rates and higher survival. Here, we investigated whether some of these effects may be explained by female breeders reducing their investment in eggs in response to helper presence. In addition, we investigated whether egg investment is associated with the female breeder's future fitness. Our results showed that helper presence had no effect on the female breeders’ egg investment, and that egg investment was not associated with breeder survival and reproductive success. Our findings suggest that the responses of breeders to helping should be investigated throughout the breeding cycle, because the conclusions regarding the breeders’ adjustment of reproductive investment in response to being helped may depend on which stage of the breeding cycle is considered.

Rewilding cultural landscape potentially puts both avian diversity and endemism at risk: A Tibetan Plateau case study

Ecological restoration is becoming a primary strategy to increase provisions of ecosystem services and reverse biodiversity losses. In cultural landscapes undergoing land use extensification, rewilding has been proposed as a viable approach to reverse biodiversity loss through reducing human impacts. The world's largest ecological restoration campaign is taking place on the eastern Qinghai-Tibetan Plateau (QTP) to combat grassland degradation and enhance the upper stream region's water retention capacity. However, little is known about whether the large-scale rewilding also benefits the unique bird assemblage of the eastern QTP. Our study aims to make science-based conservation recommendations for the Tibetan avifauna by detecting their diversity and endemism distribution patterns at the local scale. In the breeding seasons of 2014 and 2015, we carried out bird surveys and conducted a habitat mapping using three Unmanned Aerial Vehicles (UAVs). We developed a comprehensive set of 2D and 3D habitat feature parameters from the high-resolution (10 cm level) UAV-derived images. Meanwhile, we employed the participatory GIS approach to acquire farm-scale human land-use data. Our results indicate that the distributions of avian diversity, endemism and abundance are not congruent across the eastern QTP, which calls for the conservation of different habitat types. Vertical and horizontal habitat heterogeneity maintain the local bird diversity with anthropogenic elements significantly enriching the overall bird abundance. Degraded pastures provided key habitats for two highly abundant endemic passerines—the White-rumped Snowfinch Onychostruthus taczanowskii and the Ground Tit Pseudopodoces humilis. At the landscape scale, historical human-nature interactions between Tibetan nomads and the alpine environment formed the landscape's patchy vegetation structure. Our results reveal that the Tibetan cultural landscape maintains the structural heterogeneity needed to achieve multiple bird conservation objectives on the eastern QTP. Restoring the cultural landscape to a ‘natural’ tall-grass or dense-shrubland state of high water-retention capacity may result in the loss of both high-abundance avian communities and endemic species diversity. Our empirical study also indicated that rewilding abandoned agricultural landscape will not necessarily lead to a desired conservation outcome, especially when the requirements of habitat specialists and endemics are not taken into account. Moreover, ecological restoration projects should evaluate the divergences between their ecosystem service and biodiversity objectives.

Hamilton's inclusive fitness maintains heritable altruism polymorphism through rb = c

How can altruism evolve or be maintained in a selfish world? Hamilton's rule shows that the former process will occur when rb > c-the benefits to the recipients of an altruistic act b, weighted by the relatedness between the social partners r, exceed the costs to the altruists c-drives altruistic genotypes spreading against nonaltruistic ones. From this rule, we infer that altruistic genotypes will persist in a population by forming a stable heritable polymorphism with nonaltruistic genotypes if rb = c makes inclusive fitness of the two morphs equal. We test this prediction using the data of 12 years of study on a cooperatively breeding bird, the Tibetan ground tit Pseudopodoces humilis, where helping is performed by males only and kin-directed. Individual variation in ever acting as a helper was heritable (h2 = 0.47), and the resultant altruism polymorphism remained stable as indicated by low-level annual fluctuation of the percentage of helpers among all adult males (24-28%). Helpers' indirect fitness gains from increased lifetime reproductive success of related breeders statistically fully compensated for their lifetime direct fitness losses, suggesting that rb = c holds. While our work provides a fundamental support for Hamilton's idea, it highlights the equivalent inclusive fitness returns to altruists and nonaltruists mediated by rb = c as a theoretically and realistically important mechanism to maintain social polymorphism.

Social organization, demography and genetic mating system of a Tibetan cooperative breeder

Knowledge of cooperative breeding in birds from longitudinal studies is available only for a small proportion of species. This paper reports data from a 12‐year study on the Tibetan Ground Tit Pseudopodoces humilis. On average, 27.2% (range: 13.0–36.1%) of monogamous pairs in each year contained one (85.4%) or more (14.6%) male helpers, 83.7% of which were yearlings staying on natal territories. Most helpers (89.6%) helped once and then bred independently. Adults had male‐biased sex ratios, low annual survival rates (averaging 0.50) and shorter longevities (averaging 1.8 years) compared with low‐altitude avian cooperative breeders, suggesting that mate shortage promotes helping behaviour in this species. Incest occurred rarely (2.1% of pairs), probably because kin recognition occurs through year‐around living in family groups. There was a low level (3.1% of broods) of extra‐pair parentage, which could facilitate the maintenance of cooperative breeding.

Nest helpers improve parental survival but not offspring production in a high‐elevation passerine, the Ground Tit Pseudopodoces humilis

The way in which breeders respond to helping, in terms of either offspring production or their own survival, may reflect the adaptive aspects of a cooperative breeding system. We explore this issue using a 5‐year study of the Ground Tit Pseudopodoces humilis, a facultative cooperative breeder in which 47% of socially monogamous pairs have between one and four close male relatives as helpers. We found that helped nests did not fledge more or heavier nestlings than unhelped nests, and male young from helped and unhelped nests were equally likely to recruit into the local breeding population. However, helped parents of both sexes had a higher probability of survival to the following year than did unhelped parents. These findings suggest that Ground Tit parents with helpers trade current reproduction for personal survival and future reproduction, a strategy favoured by selection to cope with harsh, unpredictable environments such as the Tibetan Plateau.

Correction: The genome sequence of the ground tit Pseudopodoces humilis provides insights into its adaptation to high altitude

1. Fumin Lei is no longer listed as an author of this article. Instead, his helpful input is noted in the acknowledgements section. 2. The provisional version of this article mistakenly stated that zebra finch belongs to the Paridae family. We have now corrected this error to reflect the classification of this species to the Estrildidae family. 3. In the abstract of the provisional version of the article we stated that the phylogeny of the ground tit was confirmed as belonging to the Paridae family. We have now re-phrased this sentence to say that ground tit phylogeny was confirmed as not belonging to the Corvidae family. 4. In the conclusions of the provisional version of the article we stated that the phylogeny of the ground tit was confirmed as not belonging to the Corvidae family but to the Paridae family. We have now re-phrased this conclusion to say that ground tit phylogeny was confirmed as not belonging to the Corvidae family.

Genome sequence of ground tit Pseudopodoces humilis and its adaptation to high altitude

BackgroundThe mechanism of high-altitude adaptation has been studied in certain mammals. However, in avian species like the ground tit Pseudopodoces humilis, the adaptation mechanism remains unclear. The phylogeny of the ground tit is also controversial.ResultsUsing next generation sequencing technology, we generated and assembled a draft genome sequence of the ground tit. The assembly contained 1.04 Gb of sequence that covered 95.4% of the whole genome and had higher N50 values, at the level of both scaffolds and contigs, than other sequenced avian genomes. About 1.7 million SNPs were detected, 16,998 protein-coding genes were predicted and 7% of the genome was identified as repeat sequences. Comparisons between the ground tit genome and other avian genomes revealed a conserved genome structure and confirmed the phylogeny of ground tit as not belonging to the Corvidae family. Gene family expansion and positively selected gene analysis revealed genes that were related to cardiac function. Our findings contribute to our understanding of the adaptation of this species to extreme environmental living conditions.ConclusionsOur data and analysis contribute to the study of avian evolutionary history and provide new insights into the adaptation mechanisms to extreme conditions in animals.

Bi‐parental vs. cooperative breeding in a passerine: fitness‐maximizing strategies of males in response to risk of extra‐pair paternity?

In socially monogamous species, males that risk cuckoldry more than others might gain inclusive fitness by yielding paternity to relatives. We tested this prediction in the Tibetan ground tit Pseudopodoces humilis, an unusual facultative cooperative breeder wherein most helpers (87% males) join a mated pair shortly before clutch completion. Extra-pair paternity among bi-parental broods occurred less often (26% of broods, 9% of young) compared with cooperative broods (68%, 25%). In the former, most extra-pair sires (88%) were pair breeders unrelated to the cuckolded males, whereas in the latter, sires (87%) were mainly helpers related to the dominant males. Brood productivity did not differ between the bi-parental and cooperative breeders, but helpers' partitioning over group paternity reduced the realized reproductive success of helped males. After taking inclusive fitness into account, however, there was no difference in success of dominant males between the two social systems. One possible explanation for the differences in the rates of cuckoldry in the two systems was body size, because pair-bond males in bi-parental situations were significantly larger than those in cooperative ones. We propose two alternative strategies for males to maximize fitness: breed as a pair if large to avoid cuckoldry from helpers, or breed cooperatively if small but compromise some paternity to relatives. Our results provide an unusual route to the incidence of cooperative groups, based on constraints imposed by low competitive ability of breeding males rather than some external ecological or demographic factors.

Burrow use by Tibetan Ground Tits Pseudopodoces humilis: coping with life at high altitudes

The Tibetan Ground Tit Pseudopodoces humilis is a high‐altitude passerine endemic to the Tibetan Plateau. A 4‐year study in alpine meadows in Northern Tibet at 4300 m asl demonstrated that rather than using Pika Ochotona spp. holes as previously reported, the birds excavated one nest burrow themselves in spring and another after breeding, which they used for roosting in winter. Both the nesting and winter‐roosting burrows comprised a straight tunnel leading to an ellipsoid chamber. There were no significant differences in placement or structural characteristics between the two types of burrows, except that winter‐roosting burrows had a significantly smaller entrance diameter. Most burrows were 100–160 cm long and their chambers 20–40 cm deep. Tibetan Ground Tits tended to maximize the thermal benefits of their burrows by adjusting their spatial and structural characteristics in response to local solar radiation and wind regimes. Burrows tended to be oriented towards the sun and away from prevailing winds, presumably to maintain burrow temperature. Longer tunnels could function to save heat from solar radiation or reduce wind‐disturbance, while shorter tunnels allow chambers to be warmed sooner in situations where wind potentially reduced soil temperatures. The thermal benefits to the birds of burrow architecture are likely to play a crucial role throughout the year in these extreme alpine environments.