Evolution in a tropical archipelago: comparative phylogeography of Philippine fauna and flora reveals complex patterns of colonization and diversification

An unusual geological setting and a high level of endemism makes the Philippine islands of great interest to biogeography. These islands lie adjacent to the continental (Sunda) shelf, yet the majority of the islands have never been directly attached to the mainland. Existing hypotheses of colonization and diversification processes have been tested across multiple taxa, but only in ahistorical contexts. We present explicit phylogenetic predictions based on these hypotheses, and then test them using new molecular datasets for four Philippine birds. Two proposed colonization routes to the northern Philippines (from mainland Asia and Palawan) are difficult to differentiate from each other, except on the basis of outgroup, as are the two routes from the south (Sulu archipelago and Sulawesi). We find unique colonization and diversification patterns for each taxon. These results contrast with expectations from Pleistocene geography, with Luzon and Mindoro indistinguishable genetically, and Negros and Panay are often nonsister taxa. Combining these data with a literature search for studies addressing these patterns, Philippine organisms shows some evidence for each proposed colonization route but the greatest support is for the two routes from Borneo. Many taxa exhibit multiple colonization events using several of these routes, contrasting with past assumptions of single colonization events. Island‐by‐island differentiation within the Philippines follows, with patterns reflecting colonization patterns rather than Pleistocene geography, particularly for highland species. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 620–639.     

Montane forest birds in winter: do they regularly move to lower altitudes? Observations from the Eastern Cape,South Africa

Seasonal altitudinal migration to lower altitudes including the coast has been ascribed to a number of forest birds, of which 14 species occur at Fort Fordyce Reserve in the Eastern Cape, South Africa. Based on our observations and ringing at this site (2007–2017), as well as concurrent data from the South African Bird Atlas Project (SABAP2), we suggest that in this region only three species, the African Dusky Flycatcher Muscicapa adusta, White-starred Robin Pogonocichla stellata and Barratt's Warbler Bradypterus barratti, are regular altitudinal migrants. For two other species, the Grey Cuckooshrike Coracina caesia and Yellow-throated Woodland Warbler Phylloscopus ruficapilla, local movements apparently occur, but these may take place within the coastal zone rather than between the coast and inland forests.     

以鸟类视觉模型揭示中杜鹃对冠纹柳莺的卵色模拟(英文)

于2009年4—7月,采用光谱仪量化卵色和建立鸟类视觉模型的方法,在贵州宽阔水自然保护区对中杜鹃(Cuculus saturatus)寄生冠纹柳莺(Phylloscopus reguloides)的卵色模拟进行了研究。中杜鹃产白色卵带极少数而微小的棕色斑,明显大于宿主卵,重2.06g,体积1.91cm3。从人眼看,中杜鹃卵对宿主卵在很大程度上是模拟的,但视觉模型表明,两者的卵色在色调和色度上都完全分离,揭示了人眼探测不到的卵色模拟情况。该文首次对中杜鹃的雏鸟特征进行描述,在4日龄以后雏鸟嘴裂中出现三角形黑斑,并随着日龄的增长而更加明显,这种特征在霍氏中杜鹃(C.optatus)的雏鸟中也存在,但未见于其他种类的杜鹃雏鸟。     

Incipient ring speciation revealed by a migratory divide

Ever since Ernst Mayr (1942) called ring species the ‘perfect demonstration of speciation’, they have attracted much interest from researchers examining how two species evolve from one. In a ring species, two sympatric and reproductively isolated forms are connected by a long chain of intermediate populations that encircle a geographic barrier. Ring species have the potential to demonstrate that speciation can occur without complete geographic isolation, in contrast to the classic model of allopatric speciation. They also allow researchers to examine the causes of reproductive isolation in the contact zone and to use spatial variation to infer the steps by which speciation occurs. According to the classical definition, a ring species must have (i) gradual variation through a chain of populations connecting two divergent and sympatric forms, and (ii) complete or nearly complete reproductive isolation between the terminal forms. But evolutionary biologists now recognize that the process of speciation might often occur with some periods of geographic contact and hybridization between diverging forms; during these phases, even partial reproductive isolation can limit gene flow and permit further divergence to occur. In this issue Bensch et al. (2009) make an exciting and important contribution by extending the ring species concept to a case in which the divergence is much younger and not yet advanced to full reproductive isolation. Their study of geographic variation in willow warblers (Phylloscopus trochilus; Fig. 1 ) provides a beautiful example of gradual variation through a ring of populations connecting two forms that are partially reproductively isolated where they meet, possibly due to divergent migratory behaviours of the terminal forms.

Figure 1 Open in figure viewer PowerPoint A male willow warbler resembling the southeastern‐migrating form (Phylloscopus trochilus acredula), on its breeding territory in central Sweden. (Photo: Anders Hedenström).     

The use of AFLP to find an informative SNP: genetic differences across a migratory divide in willow warblers

We used the amplified fragment length polymorphism (AFLP) method to obtain genetic markers distinguishing two subspecies of willow warblers Phylloscopus trochilus that have different migratory behaviours but are not differentiated in mitochondrial DNA or at several microsatellite loci. With the inverse-polymerase chain reaction (PCR) approach we converted a dominant AFLP-marker to a codominant single nucleotide polymorphism (SNP). Across Scandinavia we typed 621 birds at the SNP locus AFLP-WW1 and we found a sigmoid change in allele frequencies centred around 62 degrees latitude. North of the latitudinal cline was a west-east cline. Both clines are narrower than one would expect from dispersal distances in willow warblers, which suggests that these are maintained by selection. The latitudinal cline at the locus AFLP-WW1 is paralleled by changes in several other traits, all of which might be maintained by a single selective force. The most plausible selection factor that we have identified is selection against hybrids because of inferior migratory behaviour. The selective force maintaining the east-west cline is less obvious. We discuss alternatives to the selection scenario, involving colonization history and asymmetric gene flow.     

Annual variation in fat storage by a migrant warbler overwintering in the Indian tropics

1. We studied fat storage in a population of greenish leaf warblers ( Phylloscopus trochiloides ) in southern India over four winters (1993–97). This species breeds in temperate regions and overwinters in India from October to April.
2. Diurnal variation in fat scores was comparable to that seen among temperate wintering passerines. Seasonal variation was slight, except for premigratory fattening. There was significant annual variation: in drier winters, which were also winters of low food supplies, fat scores were higher.
3. Energy metabolized overnight is unlikely to vary across winters, and annual variation in fat scores is considered a response to uncertainty of food intake on a given day. Fat scores varied inversely with short-term rainfall, which drives the abundance of arthropod prey.
4. Annual variation in fat scores was not accompanied by changes in total body mass. This suggests that protein reserves were being compromised by increased fat deposition in dry years and offers an explanation for the observed delay in moult during drier winters. These results suggest that strategies for maximizing short-term probability of survival translate into future fitness costs, and may shape long-term life-history strategies through simple physiological processes.     

近10年秦皇岛两种鸟类春季迁徙 时间变化的差异性

气候变化对鸟类迁徙时间的影响是目前生态学研究的热点问题。本文利用鸟类环志的方法分析了2010至2019年河北秦皇岛两种鸟类春季迁徙时间变化趋势及其差异性,并进一步探讨了差异性的原因。选择环志数量较多的食虫鸟黄眉柳莺(Phylloscopus inornatus)和食谷鸟灰头鹀(Emberiza spodocephala)作为研究对象,分析了10年间两种鸟类春季迁徙到达时间、高峰期、离开时间和停歇天数的变化及其相关性。结果表明,10年间黄眉柳莺和灰头鹀春季迁徙到达时间、高峰期和离开时间都出现了提前现象。黄眉柳莺和灰头鹀在秦皇岛停歇天数都呈现缩短的趋势,黄眉柳莺到达时间与离开时间存在显著的正相关。两种候鸟春季迁徙时间出现这种变化的原因是由于秦皇岛环境温度呈现逐渐升高的趋势,促使各种植被群落和昆虫提前进入生长繁殖阶段,为春季提前迁徙而来的候鸟提供丰富的食物资源。黄眉柳莺春季迁徙期在秦皇岛采取“早到早走”的策略,提早到达繁殖地可以增加其繁殖成功率,有助于提高鸟类种群的生存率。     

Composition and diversity of bird communities in Swedish farmland–forest mosaic landscapes

CapsuleThe amount of forest (at local and landscape scales) and occurrence of residual habitats at the local scale are shown to be the major factors influencing bird community composition in farmland–forest landscapes in central Sweden.

Aims To investigate the importance of local habitat and landscape structure for breeding birds in farmland–forest landscapes in central Sweden.

Methods Breeding birds were censused at 292 points. A detailed habitat mapping was made within 300 m of the points. Within a 300–600 m radius only two major habitats (forests and arable fields) were identified.

Results Cluster analyses of bird communities identified three site types that also differed in habitat composition: (i) partially forested sites in forested landscapes; (ii) heterogeneous sites with residual habitats in mosaic landscapes; and (iii) field-dominated farmland sites in open landscapes. A total of 19 of 25 farmland bird species (restricted to farmland or using both farmland and forest) had the highest abundance in farmland sites with mosaics of forest and farmland, while only six farmland species had the highest abundance in field-dominated sites. The bird community changed from being dominated by farmland species to being dominated by forest species (common in forest landscapes without farmland) at small proportions (10–20%) of forest at the local scale. A major difference in habitat composition between heterogeneous and field-dominated sites was the occurrence of different residual habitats (e.g. shrubby areas and seminatural grasslands). These habitats seemed to influence bird community composition more than land-use, despite covering <10% of the area. Seminatural grasslands were important for bird community composition and species-richness, but grazing seemed to be less important. Among different land-use types, cereal crops were the least preferred fields. Set-asides with tall vegetation and short rotation coppices were positively associated with species-richness of farmland birds.

Conclusion In general, the composition of the landscape was important for bird community composition, although amount and distribution of forests, occurrence of residual habitats and land-use of fields at the local scale had the strongest influence on bird community composition. The possible implications of these patterns for managing farmland–forest landscapes are discussed.     

Observer variation in estimates of Meadow Pipit Anthus pratensis and Skylark Alauda arvensis abundance on moorland

Capsule Counts least susceptible to observer effects were those within 25 m of a transect and the total number along a transect, with observer effects greater for distance sampling.     

Causes of the latitudinal gradient in birdsong complexity assessed from geographical variation within two Himalayan warbler species

Aspects of birdsong complexity, such as the number of distinct notes in a song, commonly increase along latitudinal gradients, a pattern for which at least 10 explanations have been suggested. In two Himalayan warblers, songs are more complex in the northwest than in the southeast. In Grey‐hooded Warbler Phylloscopus xanthoschistos, high complexity results from increased note diversity within song types, sung across a higher bandwidth. In Blyth's Leaf Warbler Phylloscopus reguloides, high complexity is a consequence of increased variation between song types. The hypothesis with strongest support is that songs evolved to be more complex in species‐poor, demonstrably less noisy environments. We consider geographical variation to be an outcome of sexual selection favouring complexity across environments, where detection of the signal varies. Sexual selection favouring complexity may be resolved in different ways, because complexity has multiple features (repertoire size, song switching, etc.). We argue this has led to the great diversity in song that we have documented among five Phylloscopus species.