Sex ratio and morphological characteristics of rufous gnateaters, Conopophaga lineata (Aves, Passeriformes) in Atlantic forest fragments

Abstract

ABSTRACT. Unequal sex ratios lead to the loss of genetic variability, decreasing the viability of populations in the long term. Anthropogenic activities often disturb the natural habitats and can cause alterations in sex ratio and morphological characteristics of several species. Forest fragmentation is a major conservation concern, so that understanding its effects in natural populations is essential. In this study, we evaluated the sex ratio and the morphological characteristics of Rufous Gnateaters (Conopophaga lineata (Wied, 1831)) in small and large forest fragments in Minas Gerais, Brazil. Birds (n = 89) were sexed by plumage characteristics and molecular markers. The molecular analysis showed that plumage is not a totally reliable method for sexing Rufous Gnateaters. We observed that sex ratio did not differ between large and small forest fragments, but birds in small fragments had larger wings and tarsus. Wing and tarsus changes may affect the movement ability of individuals within and among forest fragments. In conclusion, Rufous Gnateaters have been able to survive in both small and large Atlantic rain forest fragments without altering their sex ratio, but morphological changes can be prejudicial to their long term survival. KEYWORDS.Forest fragmentation, sex ratio, Atlantic forest, Conopophagidae. RESUMO.Razão sexual e características morfológicas do chupa-dente, Conopophaga lineata (Aves, Passeriformes) em fragmentos da Mata Atlântica. A razão sexual desigual pode levar à perda de variabilidade genética, diminuindo a viabilidade das populações em longo prazo. Atividades antrópicas causam alterações nos hábitats e podem causar mudanças na razão sexual e na morfologia de muitas espécies. A fragmentação florestal é uma grande preocupação em conservação e entender os seus efeitos em populações naturais é fundamental. Assim, neste estudo buscamos investigar a razão sexual e algumas características morfológicas do chupa-dente (Conopophaga lineata (Wied, 1831)) em fragmentos pequenos e grandes no Estado de Minas Gerais, Brasil. As aves (n = 89) foram sexadas através de características da plumagem e através de marcadores moleculares. Marcadores moleculares indicaram que a identificação por plumagem não é um método totalmente confiável para essa espécie. Observamos que a razão sexual não difere entre os fragmentos grandes e pequenos, mas os indivíduos dos fragmentos pequenos apresentaram asas e tarsos maiores. Modificações nas asas e tarsos podem causar alterações no deslocamento dos indivíduos dentro e entre os fragmentos. Portanto, os chupa-dentes têm sido capazes de sobreviver mesmo nos pequenos fragmentos de Mata Atlântica sem sofrer alterações na razão sexual. Porém, as diferenças morfológicas apresentadas podem ser prejudiciais para a sobrevivência da espécie a longo prazo. PALAVRAS-CHAVE.Fragmentação florestal, razão sexual, Mata Atlântica, Conopophagidae.

Full Issue

“…Small sample sizes and studies conducted solely in small forest fragments or human-modified environments can bias reproductive success (Oniki 1979, Martin 1996. At least C. lineata appears to respond well to forest fragmentation, surviving in small fragments without significant changes in sex ratio (Dantas et al 2009) or nesting capacity (Marini et al 2007) despite morphological alterations being reported (Anciães & Marini 2000, Dantas et al 2009. However, in a small forest fragment, Willis et al (1983) found three infertile eggs in two of four monitored nests of the species; inbreeding and insecticides used in nearby crop fields were hypothesised as possible causes.…”

Additional breeding data for Ceará Gnateater Conopophaga cearae, with a review of the breeding biology of the Conopophagidae

“…Small sample sizes and studies conducted solely in small forest fragments or human-modified environments can bias reproductive success (Oniki 1979, Martin 1996). At least C. lineata appears to respond well to forest fragmentation, surviving in small fragments without significant changes in sex ratio (Dantas et al . 2009) or nesting capacity (Marini et al .…”

Fluctuating Asymmetry and Environmental Stress: Understanding the Role of Trait History

“…However, indirect evidence for such association stems from a series of studies on a small understory passerine bird of fragmented Brazilian Atlantic rainforest. Rufous gnateaters ( Conopophaga lineata ) that were captured in tiny rainforest fragments showed both larger [30] and more asymmetric [1] wings compared to conspecifics captured in larger forests, and the shift in trait size was interpreted as an adaptation to disperse among poorly-connected forest fragments [30]. While the underlying developmental mechanism(s) remain to be tested in our study (as is the case for most processes related to FA; [6]), the fact that enlarged traits showed higher levels of FA than traits that decreased in size, suggests that high growth rates may have compromised mechanisms controlling early trait development [33], [34].…”

“…98% over the last 200 years, as a result of agricultural expansion, logging, pole cutting and cattle grazing, and formerly continuous tracts of rainforest became subdivided in small, isolated fragments, most strongly so since the early 1960s [25]–[27]. Based on 18 years of demographic, genetic and dispersal data from eight forest-restricted bird species [28], [29], it was earlier shown that this decrease in landscape connectivity resulted in a significantly loss in mobility over time in some species, while others seemed to cope better, possibly as a result of phenotypic and/or behavioural adaptations ([28]; see also [30], [31]). In addition to landscape-level effects on mobility, species also varied in their sensitivity to patch-level forest degradation, as inferred from historic changes in tarsus FA between museum specimens (collected prior to degradation) and post-degradation live captures from the same localities [32].…”