Double-brooding and annual breeding success of great tits in urban and forest habitats

Urban areas differ from natural habitats in several environmental features that influence the characteristics of animals living there. For example, birds often start breeding seasonally earlier and fledge fewer offspring per brood in cities than in natural habitats. However, longer breeding seasons in cities may increase the frequency of double-brooding in urban compared to non-urban populations, thus potentially increasing urban birds’ annual reproductive output and resulting in lower habitat difference in reproductive success than estimated by studies focusing on first clutches only. In this study, we investigated two urban and two forests great tit Parus major populations from 2013 to 2019. We compared the probability of double-brooding and the total number of annually fledged chicks per female between urban and forest habitats, while controlling for the effects of potentially confounding variables. There was a trend for a higher probability of double-brooding in urban (44% of females) than in forest populations (36%), although this was not consistent between the two urban sites. Females produced significantly fewer fledglings annually in the cities than in the forest sites, and this difference was present both within single- and double-brooded females. Furthermore, double-brooded urban females produced a similar number of fledglings per season as single-brooded forest females. These results indicate that double-brooding increases the reproductive success of female great tits in both habitats, but urban females cannot effectively compensate in this way for their lower reproductive output per brood. However, other mechanisms, like increased post-fledging survival can mitigate habitat differences in reproductive success.

The Functional Morphology of Avicularia in Cheilostome Bryozoans

<p>Avicularia are modified zooids characteristic of cheilostome bryozoans. Through evolutionary time the functional capacity of the polypide has evolved and is now a vestigial feature within the avicularium. The functional role of avicularia in the colony is unclear. Unable to feed, avicularia are dependent on nutrients from the parental or neighbouring zooids and therefore constitute a significant metabolic cost in production and maintenance, a cost which must be met by some reciprocal function. Details on the functional morphology of avicularia are severely lacking with avicularia constituting a large gap in the knowledge of cheilostome biology. By examining their biology, this study will enhance our understanding of the evolution and functional capacity of avicularia. Fundamentally this study will provide insight into the degree of morphological and morphometric divergence among avicularia. The objective of this study was to: (1) conduct a morphological survey of the putative sensory structures associated with the palate (or orificial structures) of avicularia (SEM); (2) conduct an ultrastructural-level study (TEM) of the vestigial polypide from two species of bugulids from disparate habitats; and (3) incorporate a holistic study on the behaviour and functional evolution of character traits in Bugula flabellata. The avicularia from 38 species of cheilostome bryozoans were examined covering 11 superfamilies, 18 families and 29 genera. The results indicate that avicularia are morphologically diverse and display extensive variation in avicularian orifice morphology. Structures associated with the orifice varied from tufts of cilia, simple pores, tubular protuberances, and pores with an organic exude. The adventitious avicularia dominated (83%) and displayed the greatest morphometric diversity compared with interzooidal, vicarious and vibracular types. Within superfamilies, only the catenicellids displayed a significant level of morphometric and anatomical congruence. The density of avicularia within a colony was greatest by combining adventitious and vibracular types (e.g. Caberea). This finding may represent an evolutionary shift towards maximisation of function within a smaller spatial scale. The ultrastructure of the vestigial polypide of the subtidal B. flabellata and deep-sea Nordgaardia cornucopioides revealed disparities suggestive of differing functional roles either as a result of habitat differences or differing stages of evolutionary development. The avicularium of B. flabellata has undergone significant modification in character traits from the plesiomorphic autozooid. The current anatomy and behaviour of this avicularium provides strong evidence for a mechanoreceptive function whereby detection of tactile stimuli from passing invaders is important in the functional role of the bird's-head avicularium of B. flabellata. This study is the first to examine the functional morphology of avicularia in such detail. The techniques used in this study have never been applied to avicularia before allowing numerous features such as the muscles, orificial structures and vestigial polypide anatomy to be discerned. The results indicate that avicularia are morphologically diverse and anatomically equipped to perform a variety of functions. The morphological diversity of avicularia may be of immense ecological importance and represent differing responses to various selective pressures in the environment.</p>

The Functional Morphology of Avicularia in Cheilostome Bryozoans

<p>Avicularia are modified zooids characteristic of cheilostome bryozoans. Through evolutionary time the functional capacity of the polypide has evolved and is now a vestigial feature within the avicularium. The functional role of avicularia in the colony is unclear. Unable to feed, avicularia are dependent on nutrients from the parental or neighbouring zooids and therefore constitute a significant metabolic cost in production and maintenance, a cost which must be met by some reciprocal function. Details on the functional morphology of avicularia are severely lacking with avicularia constituting a large gap in the knowledge of cheilostome biology. By examining their biology, this study will enhance our understanding of the evolution and functional capacity of avicularia. Fundamentally this study will provide insight into the degree of morphological and morphometric divergence among avicularia. The objective of this study was to: (1) conduct a morphological survey of the putative sensory structures associated with the palate (or orificial structures) of avicularia (SEM); (2) conduct an ultrastructural-level study (TEM) of the vestigial polypide from two species of bugulids from disparate habitats; and (3) incorporate a holistic study on the behaviour and functional evolution of character traits in Bugula flabellata. The avicularia from 38 species of cheilostome bryozoans were examined covering 11 superfamilies, 18 families and 29 genera. The results indicate that avicularia are morphologically diverse and display extensive variation in avicularian orifice morphology. Structures associated with the orifice varied from tufts of cilia, simple pores, tubular protuberances, and pores with an organic exude. The adventitious avicularia dominated (83%) and displayed the greatest morphometric diversity compared with interzooidal, vicarious and vibracular types. Within superfamilies, only the catenicellids displayed a significant level of morphometric and anatomical congruence. The density of avicularia within a colony was greatest by combining adventitious and vibracular types (e.g. Caberea). This finding may represent an evolutionary shift towards maximisation of function within a smaller spatial scale. The ultrastructure of the vestigial polypide of the subtidal B. flabellata and deep-sea Nordgaardia cornucopioides revealed disparities suggestive of differing functional roles either as a result of habitat differences or differing stages of evolutionary development. The avicularium of B. flabellata has undergone significant modification in character traits from the plesiomorphic autozooid. The current anatomy and behaviour of this avicularium provides strong evidence for a mechanoreceptive function whereby detection of tactile stimuli from passing invaders is important in the functional role of the bird's-head avicularium of B. flabellata. This study is the first to examine the functional morphology of avicularia in such detail. The techniques used in this study have never been applied to avicularia before allowing numerous features such as the muscles, orificial structures and vestigial polypide anatomy to be discerned. The results indicate that avicularia are morphologically diverse and anatomically equipped to perform a variety of functions. The morphological diversity of avicularia may be of immense ecological importance and represent differing responses to various selective pressures in the environment.</p>

Ecology of a Two-barred Crossbill (Loxia leucoptera) irruption to Norway in 2019–20: altitudinal migration and interspecific habitat differences

Cover photo: A male Two-barred Crossbill (Loxia leucoptera). Photo: Frode Falkenberg. Two-barred Crossbills (Loxia leucoptera) have cyclic irruptions to Norway, but are generally uncommon and breeding is rare. Here I analyse data on a large irruption occurring in 2019–20 to assess the magnitude of the irruption and the ecological niche of the species. The irruption lasted one year, starting in July 2019 and ending in June 2020. Total numbers reported by birdwatchers to the website of the National Biodiversity Information Centre in Norway were ca. 7,000 individuals. Breeding indications were reported from nearly 100 sites. Analyses of elevation of records indicated that birds were often seen at low elevations before the breeding season in February–June, but moved to higher elevations during the breeding season. In a focal study area in SE Norway, breeding season surveys along elevational gradients indicated that Two-barred Crossbills occurred at higher elevations, and often close to summits of hills, perhaps representing preferences for more open forest habitats. Two-barred Crossbills often co-occurred with other seed-eating bird species, but presence was more closely related to numbers of Common Redpoll (Acanthis flammea), than to Eurasian Siskin (Spinus spinus) or cogeneric Common Crossbill (L. curvirostra). Similarly, the Common Redpoll also increased strongly in abundance with elevation, whereas the other two species did so to a lesser degree. These data suggest that the Two-barred Crossbill favors montane forests during the breeding season, and thereby has a different niche than the Common Crossbill which is distributed more widely across all elevations.

A Hotspot in the Romanian Black Sea: Eelgrass Beds Drive Local Biodiversity in Surrounding Bare Sediments

Ecosystem engineers create habitat and provide conditions otherwise unavailable for the development of diverse communities. In marine soft-bottoms in particular, the biodiversity sustained by a matrix of relatively uniform sediments can be drastically enhanced by the presence of ecosystem engineers such as seagrasses. Unfortunately, the influence of seagrass meadows on the diversity of surrounding sediments is often unrecognized in spite of its importance, especially in coastlines exposed to multiple sources of pollution. This study examined composition and diversity associated with a bed of Zostera noltei Hornemann, 1832, and its surrounding bare sediments in a highly urbanized coastal area of the Romanian Black Sea. Dissimilarity levels were quantified and key species driving the differences between uniform (bare) and complex (eelgrass) sedimentary habitats were identified. 48 taxa were collected and counted, with epifaunal and infaunal species each accounting for nearly half of that diversity. Abundance, richness and diversity were strikingly higher in eelgrass-associated sediments, a difference driven primarily by various species of snails, crustaceans, polychaetes and bivalves. Between-habitat differences remained significant even after the removal of epifaunal species and each dataset undergoing strong data transformation. These results suggest that even small eelgrass beds, located in the vicinity of multiple sources of stress, can act as hotspots and make a substantial contribution to local benthic diversity.

Sarcophagodes duodecima sp. nov., a new small araphid fossil diatom (Bacillariophyceae) from Lower to Middle Pleistocene sediments of Japan

A new fossil diatom species, Sarcophagodes duodecima, is described from the Lower to Middle Pleistocene Karato Formation of Himeshima Island, western Japan, based on detailed morphological observation of valves using light and scanning electron microscopes. This new species is characterized by a smaller valve length range, a wide lanceolate central area, shorter striae on the valve face, and longer striae on the mantle than other members of the genus. The new species was also found in the Lower Pleistocene Bushi Formation, central Japan, suggesting that S. duodecima sp. nov. was widely distributed in Japan during Early Pleistocene time. The species composition in the sample chosen as type suggests that the new fossil species occupied a brackish-water habitat. Differences in morphological features from closely related taxa are discussed.

Thermal stress jeopardizes carbonate production of coral reefs across the western and central Pacific Ocean

Coral reefs protect islands, coastal areas, and their inhabitants from storm waves and provide essential goods and services to millions of people worldwide. Yet contemporary rates of ocean warming and local disturbances are jeopardizing the reef-building capacity of coral reefs to keep up with rapid rates of sea-level rise. This study compared the reef-building capacity of shallow-water habitats at 142 sites across a potential thermal-stress gradient in the tropical Pacific Ocean. We sought to determine the extent to which habitat differences and environmental variables potentially affect rates of net carbonate production. In general, outer-exposed reefs and lagoonal-patch reefs had higher rates of net carbonate production than nearshore reefs. The study found that thermal anomalies, particularly the intensity of thermal-stress events, play a significant role in reducing net carbonate production—evident as a diminishing trend of net carbonate production from the western to the central tropical Pacific Ocean. The results also showed a latent spatial effect along the same gradient, not explained by thermal stress, suggesting that reefs in the western tropical Pacific Ocean are potentially enhanced by the proximity of reefs in the Coral Triangle—an effect that diminishes with increasing distance and isolation.