Lien-Siang Chou

An Extreme Case of Plant-Insect Codiversification: Figs and Fig-Pollinating Wasps

It is thought that speciation in phytophagous insects is often due to colonization of novel host plants, because radiations of plant and insect lineages are typically asynchronous. Recent phylogenetic comparisons have supported this model of diversification for both insect herbivores and specialized pollinators. An exceptional case where contemporaneous plant-insect diversification might be expected is the obligate mutualism between fig trees (Ficus species, Moraceae) and their pollinating wasps (Agaonidae, Hymenoptera). The ubiquity and ecological significance of this mutualism in tropical and subtropical ecosystems has long intrigued biologists, but the systematic challenge posed by >750 interacting species pairs has hindered progress toward understanding its evolutionary history. In particular, taxon sampling and analytical tools have been insufficient for large-scale cophylogenetic analyses. Here, we sampled nearly 200 interacting pairs of fig and wasp species from across the globe. Two supermatrices were assembled: on an average, wasps had sequences from 77% of 6 genes (5.6 kb), figs had sequences from 60% of 5 genes (5.5 kb), and overall 850 new DNA sequences were generated for this study. We also developed a new analytical tool, Jane 2, for event-based phylogenetic reconciliation analysis of very large data sets. Separate Bayesian phylogenetic analyses for figs and fig wasps under relaxed molecular clock assumptions indicate Cretaceous diversification of crown groups and contemporaneous divergence for nearly half of all fig and pollinator lineages. Event-based cophylogenetic analyses further support the codiversification hypothesis. Biogeographic analyses indicate that the present-day distribution of fig and pollinator lineages is consistent with a Eurasian origin and subsequent dispersal, rather than with Gondwanan vicariance. Overall, our findings indicate that the fig-pollinator mutualism represents an extreme case among plant-insect interactions of coordinated dispersal and long-term codiversification. [Biogeography; coevolution; cospeciation; host switching; long-branch attraction; phylogeny.].

Mitochondrial DNA analysis of sympatric morphotypes of bottlenose dolphins (genus: Tursiops) in Chinese waters

The classification within the bottlenose dolphin (genus Tursiops) is controversial. Although many morphological variants exist, most authors have concluded that the genus is composed of a single species, Tursiops truncatus (Montagu 1821). Two distinct morphotypes of bottlenose dolphins, which have been referred to as T. truncatus and T. aduncus, exist in sympatry in Chinese waters. Comparisons of a 386‐bp fragment of the mitochondrial DNA (mtDNA) control region (n = 47) indicated that the two sympatric morphotypes were genetically distinct, with seven fixed site differences and a sequence divergence of approximately 4.4%. Phylogenetic analyses using maximum likelihood, neighbour‐joining and maximum parsimony approaches showed that the truncatus‐type dolphins from Chinese waters were more closely related to Atlantic Ocean truncatus‐type than to the sympatric aduncus‐type dolphins. The Atlantic truncatus‐type dolphins also shared the same diagnostic sites that separated Chinese truncatus‐type from aduncus‐type dolphins. The molecular data agreed completely with the morphological classifications of the specimens. This congruence is strong evidence that the sympatric morphotypes in Chinese waters are reproductively isolated and comprise two distinct species. These findings have important implications for the conservation of bottlenose dolphins in Chinese waters.

Differences in the External Morphology of Two Sympatric Species of Bottlenose Dolphins (Genus Tursiops) in the Waters of China

Abstract Clear genetic and osteological characters exist to distinguish 2 sympatric species of bottlenose dolphins (genus Tursiops) in the waters of China. However, these characters are not useful for the identification of free-ranging dolphins. To determine if these species could be differentiated by external morphology, a discriminant analysis was performed on 8 external morphometric characters of 57 specimens, 40 of which were classified a priori as T. truncatus and 17 as T. aduncus using genetic, osteological, and other information. External morphological separation of the 2 species was highly significant. Furthermore, discriminant scores were nonoverlapping, and classification functions were successful in classifying several new specimens from the waters of China and Indonesia. Rostrum length as an absolute measure and as a proportion of total body length or snout-to-eye length revealed nonoverlapping distributions for the 2 species in the waters of China and thus offered useful field characters for classifying fresh carcasses, stranded individuals, captive specimens, photographs, and in some cases free-ranging individuals.

Mercury, organic-mercury and selenium in small cetaceans in Taiwanese waters

Total Hg (sigmaHg), organic-Hg (O-Hg) and Se bioaccumulations in small cetaceans distributed in Taiwanese waters of the Taiwan Strait and the southwestern Pacific have been investigated for the first time. The results could represent the baseline metal concentrations of marine mammals in the southwestern Pacific, where volcanic activities are possibly the major source of mercury to the environments. Muscle samples of four species of small cetaceans were collected from animals accidentally caught by tuna-longline fisheries from 1994 through 1995. In total, 53 pantropical spotted dolphins, Stenella attenuata, nine spinner dolphins, S. longirostris, five bottlenose dolphins, Turiops truncatus and four Rissos dolphins, Grampus giseus were analyzed. In addition, two stranded pantropical spotted dolphins were investigated. Cold vapour AAS and ICP-MS were used in the analysis of Hg and Se, respectively. Significant species difference was found in the four species of small cetaceans. Among them, the pantropical spotted dolphin showed the highest mean concentration (mg/kg wet wt.) of both sigmaHg (3.64 +/- 2.19) and O-Hg (2.79 +/- 1.23), whereas the Rissos dolphin had the highest mean concentrations of Se (1.77 +/- 1.29). There was no significant sex difference with respect to metal bioaccumulation in the samples of S. attenuata. Significant correlations between body length (BL) and sigmaHg, as well as O-Hg concentrations were observed in pantropical spotted (Sa) and spinner dolphins (Sl). The linear relationships were Sa: sigmaHg = -8.290 + 0.066BL, r = 0.421; Sl: sigmaHg = -2.735 + 0.025BL, r = 0.875; Sa: O-Hg = -3.723 + 0.036BL, r = 0.408; and Sl: O-Hg = -3.017 + 0.025BL, r = 0.870. However, a demethylation phenomenon that decreasing the percentage of O-Hg coupled with increasing levels of Se was observed when the sigmaHg concentrations in the muscle tissues of dolphins reached 4 mg/kg wet wt.

Multiple models in social transmission of food selection by Norway rats, Rattus norvegicus

Abstract To investigate how an observer rat integrates multiple diet information from several demonstrator rats, an observer rat was allowed to interact with a group of four demonstrators simultaneously for 30 min, and was then offered a two-choice preference test. Each demonstrator group member had previous experience with one of two different flavoured diets. Based on different combinations of dietary experience of demonstrators, five types of demonstrator groups were formed. The relationship between the dietary preference of an observer and the ratio of the different demonstrator types in the group was investigated with Sprague-Dawley rats (females only) and Long-Evans rats (with both sexes and two age classes) in two experiments. The preference response differed significantly between observers of five demonstrator groups, and the difference increased in proportion to the ratio of the different demonstrator types. The results suggest that direct bias could be involved in the social transmission of food selection by Sprague-Dawley rats, but no bias is involved in the Long-Evans. The strength of social transmission did not show sex and age variation. Nevertheless, the baseline innate preference seemed to be lower for male than female rats.

Comparative Analysis of the Diets of Pygmy Sperm Whales and Dwarf Sperm Whales in Taiwanese Waters

Stomach contents were analyzed of six pygmy sperm whales (Kogia breviceps) and five dwarf sperm whales (Kogia sima) which were taken as by-catch or were stranded specimens in coastal Taiwan from 1998 through 2000. Twenty-two species in 12 families of oceanic cephalopods were identified. In pygmy sperm whales, Enoploteuthis chunii, Sthenoteuthis oualaniensis, and Taonius pavo were the primary prey in the diet, while E. chunii, Histioteuthis miranda, and T. pavo were the most important prey items ingested by dwarf sperm whales. Although the primary prey items these two species ingested were very similar, each item comprised a different proportion for each whale species. A similarity test demonstrated a significant difference in prey composition, and SIMPER analysis showed that E. chunii was ranked first and contributed 37.1 % to the average dissimilarity between pygmy and dwarf sperm whales. Pygmy sperm whales fed on much larger T. pavo compared to those ingested by dwarf sperm whales, while dwarf sperm whales ingested more H. miranda than did pygmy sperm whales. These results support the view that pygmy sperm whales live seaward of the continental shelf and that dwarf sperm whales live more in coastal waters.

Phylogenetic analyses suggest a hybrid origin of the figs (Moraceae: Ficus) that are endemic to the Ogasawara (Bonin) Islands, Japan.

The Ogasawara Islands are oceanic islands and harbor a unique endemic flora. There are three fig species (Ficus boninsimae, F. nishimurae and F. iidaiana) endemic to the Ogasawara Islands, and these species have been considered to be closely related to Ficus erecta, and to have diverged within the islands. However, this hypothesis remains uncertain. To investigate this issue, we assessed the phylogenetic relationships of the Ogasawara figs and their close relatives occurring in Japan, Taiwan and South China based on six plastid genome regions, nuclear ITS region and two nuclear genes. The plastid genome-based tree indicated a close relationship between the Ogasawara figs and F. erecta, whereas some of the nuclear gene-based trees suggested this relationship was not so close. In addition, the phylogenetic analyses of the pollinating wasps associated with these fig species based on the nuclear 28S rRNA and mitochondrial cytB genes suggested that the fig-pollinating wasps of F. erecta are not sister to those of the Ogasawara figs These results suggest the occurrence of an early hybridization event(s) in the lineage leading to the Ogasawara figs.

Indeterminate Growth of the Fairy Shrimp, Branchinella (Branchinellites) kugenumaensis (Branchiopoda: Anostraca) in an Unpredictable Ephemeral Pool

Abstract A major life-history challenge for fairy shrimps (Anostraca) is the unpredictable environment of the ephemeral pool. The duration and predictability of pool inundations affects their life history strategy. The growth and reproduction schedule of a thamnocephalid fairy shrimp, Branchinella (Branchinellites) kugenumaensis, in an unpredictable ephemeral pool in northern Taiwan was monitored from 2004 to 2008. A total of 15 inundation episodes, resulting from typhoons or, occasionally, frontal systems, was recorded over the five-year period. Thirteen episodes lasted no more than 2-3 weeks. Two exceptionally long inundation periods were caused by additional rain events before the pool dried out. We recorded the growth patterns, egg spawning time, and clutch size of each fairy shrimp cohort during each inundation episode. No significant differences were observed in either growth or reproductive pattern from hatching to first spawning between short and long inundation episodes. The fairy shrimps stopped increasing in size during the first clutch production. Upon subsequent rainfall before the pool dried, the shrimp stopped reproducing and resumed growth, demonstrating a discontinuously indeterminate growth pattern, before resuming egg production. Body length was positively correlated with clutch size, and this can be expressed as clutch size  =  0.0059 body length3.165. The potential reproductive fitness of this indeterminate growth strategy demonstrates optimal resource allocation between growth and reproduction.

Seasonal Distribution of Indo-Pacific Humpback Dolphins at an Estuarine Habitat: Influences of Upstream Rainfall

River estuaries are dynamic regions that are influenced by the interactions between freshwater and seawater as well as seasonal variations in river runoffs. Studies focusing on the distribution of Indo-Pacific humpback dolphins (Sousa chinensis) have indicated their general tendency toward estuarine habitats. The seasonal activities of humpback dolphins are likely to synchronize with environmental fluctuations. This study investigated the effects of seasonal changes in river runoffs on the distribution gradient of humpback dolphins by deploying acoustic data loggers along the Xin Huwei River estuary, Western Taiwan, between July 2009 and September 2012. Seasonal shifts were observed in the areas with high detected duration of humpback dolphins, which mainly stayed near the river mouth during the dry seasons but moved seaward during rainy seasons and following heavy rainfall. In addition, the gradient of ambient ultrasonic pulses, dominated by snapping shrimp sounds, exhibited regional differences following heavy rainfall. The outward movements of the humpback dolphins and the snapping shrimp sounds in the estuary indicated a temporary trophic-system shift in response to local environmental changes resulting from high volumes of river runoffs. In the future, the seasonal variation in the distribution of humpback dolphins must be considered during the conservation management of this critically endangered population.

Bioaccumulation of persistent organic pollutants in stranded cetaceans from Taiwan coastal waters.

This study focuses on analyzing PBDEs in the liver, muscle, and blubber tissues of stranded dolphins (Stenella attenuate) on the Taiwan coast to determine and compare the PBDE levels and distributions among tissue types. Total concentrations of 19 PBDEs (ΣPBDE) in male dolphins (9.97 to 436ng/g fat) were significantly higher than in female animals (2.73 to 89.5ng/g fat), implying gender variation in bioaccumulation and the possibility of generation transfer from mother to fetus during pregnancy. The levels of contamination varied among tissue type; contamination was higher in blubber than that in muscle or liver, suggesting a possible transformation and redistribution of these compounds in body burden. Aside from gender and tissue type, ΣPBDE concentrations also significantly correlated with body length, an indicator of dolphin age. PCA analysis results showed no significant difference in PBDE congener pattern distributions in blubber tissues, indicating that blubber may be the final storage of contaminants in cetaceans, and that bioaccumulation of PBDEs may be dependent on chemical properties. BDE-154 and BDE-47 were the predominant PBDE congeners in stranded dolphins, and their correlation with body length suggests the significant metabolic depletion of BDE-154 in this species and possible exposure to both penta-BDE and octa-BDE mixtures.