Domain randomization-enhanced deep learning models for bird detection.

Automatic bird detection in ornithological analyses is limited by the accuracy of existing models, due to the lack of training data and the difficulties in extracting the fine-grained features required to distinguish bird species. Here we apply the domain randomization strategy to enhance the accuracy of the deep learning models in bird detection. Trained with virtual birds of sufficient variations in different environments, the model tends to focus on the fine-grained features of birds and achieves higher accuracies. Based on the 100 terabytes of 2-month continuous monitoring data of egrets, our results cover the findings using conventional manual observations, e.g., vertical stratification of egrets according to body size, and also open up opportunities of long-term bird surveys requiring intensive monitoring that is impractical using conventional methods, e.g., the weather influences on egrets, and the relationship of the migration schedules between the great egrets and little egrets.

Spatial ecology of little egret (Egretta garzetta) in Hong Kong uncovers preference for commercial fishponds.

Many natural wetlands have been converted to human-influenced wetlands. In some instances, human-influenced wetlands could provide complementary habitats for waterbirds, compensating for the loss of natural wetlands. Inner Deep Bay in Hong Kong is composed of both natural and human-influenced wetlands and is under immense development pressure. From an ecology perspective, we need to understand if different wetland types play the same ecological role. To achieve this, we tracked nine little egrets (Egretta garzetta) using GPS loggers for 14 months to study their spatial ecology, home range, movement and habitat use. We found that over 88% of the home range of all individuals comprised of wetlands (commercial fishponds, mangrove, gei wai, channel, and intertidal mudflat). Among these wetland types, nearly all (seven of nine) individuals preferred commercial fishponds over other habitats in all seasons. Little egrets exhibited seasonal movement and habitat use among seasons, with largest home range, greatest movement, and most frequent visits to commercial fishponds in winter compared to spring and autumn. Our results highlight the significant role of commercial fishponds, providing a feeding ground for little egrets. However, other wetland types cannot be ignored, as they were also used considerably. These findings underscore the importance of maintaining a diversity of wetland types as alternative foraging and breeding habitats.

Stigmatic exudate in the Annonaceae: Pollinator reward, pollen germination medium or extragynoecial compitum?

Although "dry-type" stigmas are widely regarded as ancestral in angiosperms, the early-divergent family Annonaceae has copious stigmatic exudate. We evaluate three putative functions for this exudate: as a nutritive reward for pollinators; as a pollen germination medium; and as an extragynoecial compitum that enables pollen tube growth between carpels. Stigmatic exudate is fructose dominated (72.2%), but with high levels of glucose and sucrose; the dominance of hexose sugars and the diversity of amino acids observed, including many that are essential for insects, support a nutritive role for pollinators. Sugar concentration in pre-receptive flowers is high (28.2%), falling during the peak period of stigmatic receptivity (17.4%), and then rising again toward the end of the pistillate phase (32.9%). Pollen germination was highest in sugar concentrations <20%. Sugar concentrations during the peak pistillate phase therefore provide optimal osmolarity for pollen hydration and germination; subsequent changes in sugar concentration during anthesis reinforce protogyny (in which carpels mature before stamens), enabling the retention of concentrated exudate into the staminate phase as a pollinator food reward without the possibility of pollen germination. Intercarpellary growth of pollen tubes was confirmed: the exudate therefore also functions as a suprastylar extragynoecial compitum, overcoming the limitations of apocarpy.

Time-Dependent Trapping of Pollinators Driven by the Alignment of Floral Phenology with Insect Circadian Rhythms.

Several evolutionary lineages in the early divergent angiosperm family Annonaceae possess flowers with a distinctive pollinator trapping mechanism, in which floral phenological events are very precisely timed in relation with pollinator activity patterns. This contrasts with previously described angiosperm pollinator traps, which predominantly function as pitfall traps. We assess the circadian rhythms of pollinators independently of their interactions with flowers, and correlate these data with detailed assessments of floral phenology. We reveal a close temporal alignment between patterns of pollinator activity and the floral phenology driving the trapping mechanism (termed 'circadian trapping' here). Non-trapping species with anthesis of standard duration (c. 48 h) cannot be pollinated effectively by pollinators with a morning-unimodal activity pattern; non-trapping species with abbreviated anthesis (23-27 h) face limitations in utilizing pollinators with a bimodal circadian activity; whereas species that trap pollinators (all with short anthesis) can utilize a broader range of potential pollinators, including those with both unimodal and bimodal circadian rhythms. In addition to broadening the range of potential pollinators based on their activity patterns, circadian trapping endows other selective advantages, including the possibility of an extended staminate phase to promote pollen deposition, and enhanced interfloral movement of pollinators. The relevance of the alignment of floral phenological changes with peaks in pollinator activity is furthermore evaluated for pitfall trap pollination systems.

Reproductive resource partitioning in two sympatric Goniothalamus species (Annonaceae) from Borneo: floral biology, pollinator trapping and plant breeding system.

The floral phenology, pollination ecology and breeding systems of two sympatric early-divergent angiosperms, Goniothalamus tapisoides and G. suaveolens (Annonaceae) are compared. The flowers are protogynous and morphologically similar, with anthesis over 23-25 h. Both species are predominantly xenogamous and pollinated by small beetles: G. tapisoides mainly by Curculionidae and G. suaveolens mainly by Nitidulidae. Coevolution and reproductive resource partitioning, reducing interspecific pollen transfer, is achieved by temporal isolation, due to contrasting floral phenologies; and ethological isolation, due to contrasting floral scents that contain attractants specific to the two beetle families. Analysis of floral scents revealed three volatiles (3-methylbutyl acetate, ethyl hexanoate and 2-phenylethanol) that are known to be nitidulid attractants in the floral scent of G. suaveolens, but absent from that of G. tapisoides. An effective pollinator trapping mechanism is demonstrated for both species, representing the first such report for the family. Trapping is achieved by the compression of the outer petals against the apertures between the inner petals. This trapping mechanism is likely to be a key evolutionary innovation for Goniothalamus, increasing pollination efficiency by increasing pollen loading on beetles during the staminate phase, promoting effective interfloral pollinator movements, and increasing seed-set by enabling rapid turn-over of flowers.

Drastic reduction of plastome size in the mycoheterotrophic Thismia tentaculata relative to that of its autotrophic relative Tacca chantrieri.

PREMISE OF THE STUDY: Heterotrophic angiosperms tend to have reduced plastome sizes relative to those of their autotrophic relatives because genes that code for proteins involved in photosynthesis are lost. However, some plastid-encoded proteins may have vital nonphotosynthetic functions, and the plastome therefore may be retained after the loss of photosynthesis. METHODS: We sequenced the plastome of the mycoheterotrophic species Thismia tentaculata and a representative of its sister genus, Tacca chantrieri, using next-generation technology, and we compared sequences and structures of genes and genomes of these species. KEY RESULTS: The plastome of Tacca chantrieri is similar to those of other autotrophic taxa of Dioscoreaceae, except in a few local rearrangements and one gene loss. The plastome of Thismia tentaculata is ca. 16 kbp long with a quadripartite structure and is among the smallest known plastomes. Synteny is minimal between the plastomes of Tacca chantrieri and Thismia tentaculata. The latter includes only 12 candidate genes, with all except accD involved in protein synthesis. Of the 12 genes, trnE, trnfM, and accD are frequently among the few that remain in depauperate plastomes. CONCLUSIONS: The plastome of Thismia tentaculata, like those of most other heterotrophic plants, includes a small number of genes previously suggested to be essential to plastome survival.

Functional monoecy due to delayed anther dehiscence: a novel mechanism in Pseuduvaria mulgraveana (Annonaceae).

Unlike most genera in the early-divergent angiosperm family Annonaceae, Pseuduvaria exhibits a diversity of floral sex expression. Most species are structurally andromonoecious (or possibly androdioecious), although the hermaphroditic flowers have been inferred to be functionally pistillate, with sterile staminodes. Pseuduvaria presents an ideal model for investigating the evolution of floral sex in early-divergent angiosperms, although detailed empirical studies are currently lacking. The phenology and pollination ecology of the Australian endemic species Pseuduvaria mulgraveana are studied in detail, including evaluations of floral scent chemistry, pollen viability, and floral visitors. Results showed that the flowers are pollinated by small diurnal nitidulid beetles and are protogynous. Pollen from both hermaphroditic and staminate flowers are shown to be equally viable. The structurally hermaphroditic flowers are nevertheless functionally pistillate as anther dehiscence is delayed until after petal abscission and hence after the departure of pollinators. This mechanism to achieve functional unisexuality of flowers has not previously been reported in angiosperms. It is known that protogyny is widespread amongst early-divergent angiosperms, including the Annonaceae, and is effective in preventing autogamy. Delayed anther dehiscence represents a further elaboration of this, and is effective in preventing geitonogamy since very few sexually mature flowers occur simultaneously in an individual. We highlight the necessity for field-based empirical interpretations of functional floral sex expression prior to evaluations of evolutionary processes.