Yan-Qiong Peng

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.].

Colletotrichum gloeosporioides s.l. associated with Theobroma cacao and other plants in Panamá: multilocus phylogenies distinguish host-associated pathogens from asymptomatic endophytes

Colletotrichum interacts with numerous plant species overtly as symptomatic pathogens and cryptically as asymptomatic endophytes. It is not known whether these contrasting ecological modes are optional strategies expressed by individual Colletotrichum species or whether a species’ ecology is explicitly pathogenic or endophytic. We explored this question by inferring relationships among 77 C. gloeosporioides s.l. strains isolated from asymptomatic leaves and from anthracnose lesions on leaves and fruits of Theobroma cacao (cacao) and other plants from Panamá. ITS and 5′-tef1 were used to assess diversity and to delineate operational taxonomic units for multilocus phylogenetic analysis. The ITS and 5′-tef1 screens concordantly resolved four strongly supported lineages, clades A–D: Clade A includes the ex type of C. gloeosporioides, clade B includes the ex type ITS sequence of C. boninense, and clades C and D are unidentified. The ITS yielded limited resolution and support within all clades, in particular the C. gloeosporioides clade (A), the focal lineage dealt with in this study. In contrast the 5′-tef1 screen differentiated nine distinctive haplotype subgroups within the C. gloeosporioides clade that were concordant with phylogenetic terminals resolved in a five-locus nuclear phylogeny. Among these were two phylogenetic species associated with symptomatic infections specific to either cacao or mango and five phylogenetic species isolated principally as asymptomatic infections from cacao and other plant hosts. We formally describe two new species, C. tropicale and C. ignotum, that are frequent asymptomatic associates of cacao and other Neotropical plant species, and epitypify C. theobromicola, which is associated with foliar and fruit anthracnose lesions of cacao. Asymptomatic Colletotrichum strains isolated from cacao plants grown in China included six distinct C. gloeosporioides clade taxa, only one of which is known to occur in the Neotropics.

Reinforcement of bee-plant interaction by phenolics in food

SUMMARY The winter-blooming plant Elsholtzia rugulosa produces nectar with high levels of phenolics, compounds known to both attract and deter flower visitors. In an effort to begin elucidating the interaction between phenolics and flower visitation to E. rugulosa by the native honey bee, Apis cerana, we investigated the effects of phenolic-laced sugar syrup on honey bees feeding behaviour. Honey bees fed more and foraged for immediate consumption when phenolics were presented in food. Foraging and feeding data suggest that phenolic-laced nectar is not an impediment to flower visitation by A. cerana on E. rugulosa; to the contrary, our data suggest that phenolics may increase flower visitation rate in this system.

The reproductive success of Ficus altissima and its pollinator in a strongly seasonal environment: Xishuangbanna, Southwestern China

Fig trees (Ficus spp.) are of great ecological significance, producing fruits that are fed on by more birds and mammals than any other plants in the tropics. They are pollinated by host-specific pollinator fig wasps (Hymenoptera, Agaonidae), and their fruit phenology and reproductive success are, therefore, modulated by symbiotic fig wasps. However, there are few studies focusing on the variation of Ficus reproductive success in strongly seasonal environments. We examined the phenology and reproductive success of Ficus altissima growing in a highly seasonal climate towards the northern limit of the range of fig trees in Xishuangbanna, China. Leaf production occurred at irregular intervals throughout the year, with new leaves and syconia initiated together, producing between three and seven crops over a 3-year period. Syconia were produced in synchronous crops with asynchrony between trees. The syconia produced more seeds than pollinators, and those syconia with more seeds also produced more pollinators. Reproductive success (measured as the number of seeds and pollen-carrying agaonid females produced by each syconium) varied greatly between seasons. It was highest for crops that matured during the cooler, relatively dry periods from February to March and October to November, and was lowest during the summer months from April to August. This variation corresponded to small differences in the number of flowers in the syconia, but was mainly driven by large seasonal differences in the relative abundance of non-pollinating fig wasps.

Comparison of Photosynthetic Traits Between Two Typical Shrubs: Legume and Non-Legume in Hunshandak Sandland

In Huanshandak Sandland, China, net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), intercellular CO2 concentration (Ci), water use efficiency (WUE), photochemical efficiency of photosystem 2 (Fv/Fm), and leaf nitrogen content were compared for Hedysarum fruticosum var. mongolicum (H.f.m.), a nitrogen fixing shrub, and Salix gordejevii (S.g.), a nitrogen non-fixing shrub. PN, E, and gs of the two shrubs were similar in trends, i.e. two peaks were observed in diurnal courses. However, except Ci, other parameters of H.f.m. were higher during the measured days than those of S.g. The midday depression of PN was mainly due to decrease in stomata conductance and to reduction of Fv/Fm at midday. The higher PN of H.f.m. was consistent with the higher leaf N content and there was a positive relation between them. In addition, several C4 traits were found in H.f.m., i.e. high saturation irradiance and WUE, low dark respiration rate, and Ci, which partly resulted in higher PN. This seems to indicate that the C3 plant H.f.m. may have C4 photosynthesis pathway or C4 enzymes.

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.

Diurnal variation of gas exchange, chlorophyll fluorescence, and xanthophyll cycle components of maize hybrids released in different years

Diurnal variation of gas exchange, chlorophyll (Chl) fluorescence, and xanthophyll cycle components of three maize (Zea mays L.) hybrids released in different years, i.e. Baimaya (1950s), Zhongdan2 (1970s), and Nongda108 (1990s), were compared. On cloudless days, the newer hybrids always had higher net photosynthetic rate (PN), especially at noon, than the older ones. At noon, all the hybrids decreased their maximal yield of photosystem 2 (PS2) photochemistry (Fv/Fm) and actual quantum yield of PS2 (ΦPS2), the newer ones always showing higher values. Generally, the newer hybrids displayed higher photochemical quenching of Chl (qP) and lower non-photochemical quenching (NPQ). The interhybrid differences in PN may be owing to their differential photochemical efficiency. A midday depression in PN occurred in all hybrids, which might be caused by serious photoinhibition or by decreased stomatal conductance. However, midday depression in PN was more obvious in the older hybrids, especially when leaves were senescent. The higher de-epoxidation state of the xanthophylls was noted in older hybrids, which was confirmed by their larger NPQ. The newer maize hybrids did not need a strong de-epoxidation state since they had a better photosynthetic quantum conversion rate and a lower NPQ.

The population dynamics of a non-pollinating fig wasp on Ficus auriculata at Xishuangbanna, China

All fig wasps are confined to figs as larvae, and their specialized diets are restricted to fig embryos, galled fig ovaries or other fig wasp larvae (Boucek 1988). Almost all of the ∼800 Ficus species (Moraceae) are involved in species-specific obligate mutualism with a pollinating fig wasp (Hymenoptera: Agaonidae), which also strictly depends on its host fig for reproduction (Berg 2003, Ramirez 1970, Wiebes 1979). More than half of all fig species are functionally dioecious, with male and female functions relegated to separate plants, called gall and seed figs (Kjellberg et al. 1987). Gall figs are functionally male because they foster the pollinator larvae that disperse the figs pollen as adults. Seed figs are functionally female and produce only seeds. The styles are too long for pollinator ovipositors to reach the ovules, and hence they cannot lay eggs. Gall fig styles are short (Ganeshaiah et al. 1995, Weiblen et al. 1995).

Secondary galling: a novel feeding strategy among ‘non-pollinating’ fig wasps from Ficus curtipes

The interaction between pollinator fig wasps (Agaonidae) and their host fig trees (Ficus) is a striking example of an obligate plant–insect mutualism, but figs also support numerous ‘parasites’ of the mutualism. Female agaonids (foundresses) lay their eggs in shorter‐styled flowers, whereas longer‐styled flowers produce seeds. A few ‘non‐pollinating’ fig wasps (NPFWs) can also enter figs to oviposit Fig wasp oviposition site choice and larval biology in figs of an Asian monoecious species, Ficus curtipes Corner, were recorded where two NPFW species oviposit inside the figs, such as the agaonid. Eupristina sp. agaonids chose flowers in proportion to their availability, rather than preferring to oviposit in shorter‐styled flowers. Diaziella yangi van Noort & Rasplus and Lipothymus sp. (Pteromalidae) foundresses followed Eupristina sp. into receptive figs and laid their eggs entirely in flowers that already contained pollinator eggs. This indicates that both NPFWs are inquilines under the widely‐used terminology in the fig wasp literature, because they utilise galls generated by the pollinators. However, their adult bodies and galls were larger than those of the pollinators, showing that they independently stimulate ovule growth. These species are better described as secondary gallers that modify galls previously generated by the pollinators and kill these primary gallers. Use of the term ‘inquiline’ among NPFWs inadequately and often inappropriately describes their biology. No known NPFWs are inquilines in the strict sense that they do not harm their hosts. ‘Primary gallers’, ‘secondary gallers’, ‘seed predators’, and ‘parasitoids’ describe their biology more accurately.

Reorganization of taxonomic, functional, and phylogenetic ant biodiversity after conversion to rubber plantation

Agricultural activity associated with habitat conversion is a major driver of biodiversity loss across the tropics. The decline of species richness is a common outcome of conversion to agricultural land use, but the associated changes in functional and phylogenetic diversities, and spatial patterns of beta diversity, are not well understood. These patterns may shed light on underlying ecological processes that are of both basic and applied interest; for example the relative roles of stochastic assembly, ecological filtering, and competition in structuring ecological communities as well as broader consequences for ecological functioning in agroecosystems. Here we investigate the effects of conversion to rubber plantation (Hevea brasiliensis), a rapidly spreading agroecosystem in Southeast Asia, on leaf-litter ant taxonomic, functional, and phylogenetic diversities at local and among-sites scales in Xishuangbanna, Southeast China. We found a sharp decline of ant species richness in rubber plantations compared with nearby forest habitat, with low beta diversity indicating spatial homogeneity of communities in rubber plantations. In addition, patterns of both functional alpha and beta diversities suggested the emergence of a functionally distinct ant community in the agroecosystem compared to the forest habitats. These results support a role of ecological filtering in structuring the taxonomic and functional composition of both rubber and forest habitats. In contrast, changes in phylogenetic diversity were modest and not significantly different from random expectations despite strong phylogenetic signal of functional traits. This study highlights the need for a pluralistic approach to characterizing the loss of biodiversity in agroecosystems, as well as understanding the underlying mechanisms of community assembly driving this biodiversity loss.