Raso Lark Research Articles

Selected Lark Mitochondrial Genomes Provide Insights into the Evolution of Second Control Region with Tandem Repeats in Alaudidae (Aves, Passeriformes).

The control region (CR) regulates the replication and transcription of the mitochondrial genome (mitogenome). Some avian mitogenomes possess two CRs, and the second control region (CR2) may enhance replication and transcription; however, the CR2 in lark mitogenome appears to be undergoing loss and is accompanied by tandem repeats. Here, we characterized six lark mitogenomes from Alaudala cheleensis, Eremophila alpestris, Alauda razae, and Calandrella cinerea and reconstructed the phylogeny of Passerida. Through further comparative analysis among larks, we traced the evolutionary process of CR2. The mitochondrial gene orders were conserved in all published lark mitogenomes, with Cytb-trnT-CR1-trnP-ND6-trnE-remnant CR2 with tandem repeat-trnF-rrnS. Phylogenetic analysis revealed Alaudidae and Panuridae are sister groups at the base of Sylvioidea, and sporadic losses of CR2 may occur in their common ancestor. CR sequence and phylogeny analysis indicated CR2 tandem repeats were generated within CR2, originating in the ancestor of all larks, rather than inherited from CR1. The secondary structure comparison of tandem repeat units within and between species suggested slipped-strand mispairing and DNA turnover as suitable models for explaining the origin and evolution of these repeats. This study reveals the evolutionary process of the CR2 containing tandem repeat in Alaudidae, providing reference for understanding the evolutionary characteristics and dynamics of tandem repeats.

Additional notes on butterflies of the Cape Verde Islands

Following the authors’ previously published research on Cape Verde butterflies based on fieldwork conducted in 2013, this paper presents additional data on Cape Verde butterflies as a result of further visits to the islands between 16th June and 17th July 2017, and again from 10th November to 14th December 2017. It reports three new island records (São Nicolau, Santiago and Maio) for Euchrysops osiris (Höpffer, 1855), and one new record (São Nicolau) for Junonia oenone (Linnaeus, 1758), discovered for the first time on the Cape Verde Islands (Santiago) by the authors in 2013. Occurrence of Colias croceus (Geoffroy, 1785) on Sal is discussed and a number of records for the island of Raso in the years 2015-2017 made by the Cambridge University Raso Lark survey team are presented. An updated table of Cape Verde butterflies is also presented, together with an outline map of the islands.

Lessons and surprises from an inter-island re-introduction of the critically endangered Raso Lark Alauda razae of Cape Verde

Confined to a single island where its small population fluctuates in response to rainfall, the Raso lark is likely to remain Critically Endangered unless a second population becomes established This paper reports translocations of larks, 37 in 2018 and 33 in 2019, to the nearby island of Santa Luzia where the species existed until about 500 years ago Both islands lie within the Reserva Natural Integral de Santa Luzia While the hard release protocol proceeded without mishap, problems with radio-tagging the released birds were encountered However early indications are encouraging;the released birds have bred, and their annual survival is not substantially worse than that of larks on the source island, Raso Unexpectedly, the study documented several natural, unassisted movements of larks from Raso to Santa Luzia (and, less unexpectedly, of translocated birds returning to Raso) The ultimate outcome of the project remains uncertain since eradication of Santa Luzia’s introduced cats, possible predators of the larks, was interrupted when the island was evacuated because of the Covid-19 pandemic © Paul Donald

High MHC gene copy number maintains diversity despite homozygosity in a Critically Endangered single-island endemic bird, but no evidence of MHC-based mate choice.

Small population sizes can, over time, put species at risk due to the loss of genetic variation and the deleterious effects of inbreeding. Losing diversity in the major histocompatibility complex (MHC) could be particularly harmful, given its key role in the immune system. Here, we assess MHC class I (MHC-I) diversity and its effects on mate choice and survival in the Critically Endangered Raso lark Alauda razae, a species restricted to the 7km2 islet of Raso, Cape Verde, since ~1460, whose population size has dropped as low as 20 pairs. Exhaustively genotyping 122 individuals, we find no effect of MHC-I genotype/diversity on mate choice or survival. However, we demonstrate that MHC-I diversity has been maintained through extreme bottlenecks by retention of a high number of gene copies (at least 14), aided by cosegregation of multiple haplotypes comprising 2-8 linked MHC-I loci. Within-locus homozygosity is high, contributing to low population-wide diversity. Conversely, each individual had comparably many alleles, 6-16 (average 11), and the large and divergent haplotypes occur at high frequency in the population, resulting in high within-individual MHC-I diversity. This functional immune gene diversity will be of critical importance for this highly threatened species' adaptive potential.

Genetic diversity, demographic history and neo-sex chromosomes in the Critically Endangered Raso lark.

Small effective population sizes could expose island species to inbreeding and loss of genetic variation. Here, we investigate factors shaping genetic diversity in the Raso lark, which has been restricted to a single islet for approximately 500 years, with a population size of a few hundred. We assembled a reference genome for the related Eurasian skylark and then assessed diversity and demographic history using RAD-seq data (75 samples from Raso larks and two related mainland species). We first identify broad tracts of suppressed recombination in females, indicating enlarged neo-sex chromosomes. We then show that genetic diversity across autosomes in the Raso lark is lower than in its mainland relatives, but inconsistent with long-term persistence at its current population size. Finally, we find that genetic signatures of the recent population contraction are overshadowed by an ancient expansion and persistence of a very large population until the human settlement of Cape Verde. Our findings show how genome-wide approaches to study endangered species can help avoid confounding effects of genome architecture on diversity estimates, and how present-day diversity can be shaped by ancient demographic events.

Survival of a long-lived single island endemic, the Raso lark Alauda razae, in relation to age, fluctuating population and rainfall

Estimating and understanding variation in survival rates is crucial for the management of threatened species, especially those with limited population sizes and/or restricted ranges. Using a capture-resighting dataset covering 2004–2017, we estimate adult survival in the Raso lark Alauda razae, a Critically Endangered single-island Cape Verdean endemic, whose population varied 25-fold during the study. Average annual adult survival was similar for males (0.813 ± 0.011) and females (0.826 ± 0.011) over the period. These values are high for a temperate passerine but not unusual for an insular tropical species like the lark. The oldest bird was recorded 13 years after first ringing. There was strong evidence that survival varied among years (between 0.57 and 0.95), being generally higher in wetter years. Survival, especially of males, was lower when the population was large, but only in drier years. Survival declined with age but there was no evidence that this decline was other than linear. High survival, even in the face of dry conditions, at least when the population is depressed, has probably contributed to the persistence of the species on its 7 km2 island home over several centuries.

Intricate trophic links between threatened vertebrates confined to a small island in the Atlantic Ocean.

Trophic networks in small isolated islands are in a fragile balance, and their disturbance can easily contribute toward the extinction vortex of species. Here, we show, in a small Atlantic island (Raso) in the Cabo Verde Archipelago, using DNA metabarcoding, the extent of trophic dependence of the Endangered giant wall gecko Tarentola gigas on endemic populations of vertebrates, including one of the rarest bird species of the world, the Critically Endangered Raso lark Alauda razae. We found that the Raso lark (27%), Iago sparrow Passer iagoensis (12%), Bulwer's petrel Bulweria bulwerii (15%), and the Cabo Verde shearwater Calonectris edwardsii (10%) are the most frequent vertebrate signatures found in the feces of the giant wall gecko. This work provides the first integrative assessment of their trophic links, an important issue to be considered for the long‐term conservation of these small and isolated island ecosystems.

Extreme rainfall-related clutch size variation in the Critically Endangered Raso Lark Alauda razae of the arid Cape Verde islands

SummaryThe Raso Lark Alauda razae is a single island endemic confined to the island of Raso in the Cape Verde islands. It has been studied via short (11–20 day), similarly-timed visits every year from 2001 to 2017. These November/December visits have occurred towards the end of the main rainy period (August–October) in the Cape Verdes. Average clutch size ranged from zero (no nests found) to 3.57 in different years and was strongly correlated with rainfall in the three months preceding the year’s visit, but not with population size, which varied 25-fold during the study period. Since the nomadic pursuit of rain is not an option for the Raso Lark, the species adjusts clutch size according to conditions prevailing on Raso.

Random Sample

A new tool is available to help doctors detect signs of Alzheimer's disease. According to a paper published online this week in Animal Conservation , since 2004, the population of the critically endangered Raso lark has skyrocketed from 65 to 1490. In the April 2012 issue of Sky & Telescope magazine, physicists note that a powerful spring tide may have helped push icebergs into the path of the Titanic . And this week's numbers quantify the percentage of NASA missions being extended and the number of species researchers should inventory over the next 50 years.

A scarcity of females may constrain population growth of threatened bird species: case notes from the Critically Endangered Raso Lark Alauda razae

SummaryDonald (2007) showed that the adult sex ratios of wild bird populations tended to be male-biased, and that this bias was stronger in threatened species than in those of least concern. Here we show that, in 2004, the world population of the Critically Endangered Raso Lark was 65 individuals, 70% of which were male (adult sex ratio 0.70). In 2008, the population numbered approximately 175 (including juveniles) and the adult sex ratio was 0.58. Both ratios were significantly different from parity. All adult females were observed to be both paired and holding a territory. The observations therefore support Donald’s (2007) suggestion that a shortage of females can be an important constraint on the growth of threatened bird populations, a constraint that needs attention in conservation planning.

Sexual dimorphism, niche partitioning and social dominance in the feeding ecology of the critically endangered Raso Lark Alauda razae

Sexual dimorphism, niche partitioning and social dominance in the feeding ecology of the critically endangered Raso Lark <i>Alauda razae</i>

Status of Raso Lark Alauda razae in 2003, with further notes on sex ratio, behaviour and conservation

Summary The global population of the Critically Endangered Raso Lark Alauda razae was estimated in January 2003 at 93–103 birds and in November 2003 at 76–87 birds. Of these, only 25–35% were females. Counts were based on observations of individually colour-ringed and measured birds. Birds were not breeding during the January visit, and were concentrated in two small areas at opposite ends of the island of Raso. This distribution differed substantially from that recorded previously during the breeding season. Three different feeding strategies were apparent: flocking, aggregating around key resources and feeding singly or in pairs. Birds moving to new feeding areas immediately adopted the feeding strategy of other birds present. Birds were seen drinking seawater on several occasions. In November 2003, birds were breeding but nest survival was extremely low due to high rates of egg predation. No evidence was detected of introduced predators on Raso. However, a population of feral cats was found on nearby Santa Luzia, prohibiting natural colonization or deliberate introduction of Raso Lark to the island, despite much apparently suitable habitat there. Faecal analyses showed that these cats feed largely on skinks. Increased tourism development on neighbouring islands is identified as a potential threat to the species.

Status, ecology, behaviour and conservation of Raso Lark Alauda razae

In October 2001, the world population of Raso Lark Alauda razae, confined to the uninhabited, arid islet of Raso in the Cape Verde Islands, was estimated at between 128 and 138 birds, of which 61–66% were males. The biased sex ratio was confirmed by standardized observations of randomly selected birds. The male-dominated sex ratio may result from differences in bill morphology and feeding methods. The males spent much time digging for the bulbs of the nutsedge Cyperus bulbosus, whereas females were seen to dig far less frequently. These differences may have been due to significant sexual differences in bill size. Both sexes also took a range of invertebrate prey, particularly lepidopteran larvae. Unpaired males showed differences in behaviour to paired males, particularly with respect to song flight length. Measurement of museum skins suggested significant seasonal changes in bill size, possibly related to changes in diet or feeding methods. Bill sizes in both sexes were highly variable, but significantly more variable in males. Nest predation, almost certainly by a near-endemic gecko, was extremely high, Mayfield estimates suggesting a nest survival rate of less than 5% between the onset of laying and the end of incubation. Cats and dogs were thought to be absent, although analysis of droppings shows that both have been present in the recent past. Analysis of historical data shows a strong correlation between population size and rainfall, and numbers of birds have fallen to extremely low levels during droughts. The conservation of the species is discussed in the light of these findings.

Status of Raso LarkAlauda razaewith notes on threats and foraging behaviour

The Raso LarkAlauda razaeis a globally endangered species that is endemic to the islet of Raso (16°93′ N, 24°38′ W) in the Cape Verde archipelago (Collaret al.1994). Raso is a small (c.7 km2) uninhabited islet with a plain averaging 25 m in elevation to the south and west and small boulder-strewn hills to the north and east rising up to 164 m (Figure 1). The islet comprises mostly rocky desert, with some extensive sandy patches on the western plain. Vegetation is sparse and confined to small patches on the plains and along dry river valleys.