Research interests

Sex allocation strategies and their fitness implications

Plants possess a huge variation in their sexual systems from dioecy to hermaphroditism with diverse intermediate systems. Their female and male functions are separated or combined in different modules (e.g., flowers, individuals, or stages). How and why different plants adopt such different sex-allocation strategies represents the major question in the ecology and evolution of plant sexual systems.

Sex-allocation in a perennial hermaphroditic plant

During my PhD, I have been using a perennial alpine plant, Pulsatilla alpina to address questions such as 1) how does a perennial plant adjust its sex allocation with its resource status and mating opportunities? 2) why does the species express andromonoecy (producing male and bisexual flowers at the same individual) and gender-diphasy (an individual shifts between male to hermaphrodite stages in its life)? 3) what are the tradeoffs among life-history traits?

To investigate the fitness implications of the sex allocation strategy, I conducted field experiments in the Swiss Alps to quantify the sex allocation of each individual in populations and used paternity analyses to estimate female and male reproductive success over several years.

Transition between hermaphrodite and dioecy in a wind-pollinated annual plant

I have also been using Mercurialis annua (a model system in John Pannell group) to study the transition between dioecy and hermaphroditism. Taking advantage of the phenotypes with a dramatic variation in their sex allocation as a result of artificial evolution experiments, I asked 1) how does female and male reproductive success depend on the sex allocation (i.e., the fitness gain curves)? 2) how do selfing and sexual specialization affect the transition in sexual systems? I addressed these questions using experimental gardens and again paternity analyses.

Andromonoecious Pulsatilla alpina with male and bisexual flowers

Pulsatilla alpina (Ranunculacea) is a perennial andromonoecious alpine plant. It produces bisexual (A and B) and male (C) flower in the same individual (D). The bisexual flowers are protogynous, in which the female function (A) preceeds the male function (B).

Male, female, and hermaphroditic individuals of Mercurialis annua

Phenotypes of Mercurialis annua (Euphorbiaceae) created by the artificial evolution experiments. Aalthough the species is usually dioecious in the wild, we have created hermaphrodites individuals that produce both male (blue trangle) and female (red triangle) flowers across a huge range of sex-allocation.

Ecology and evolution of reproductive traits: both female and male components

Flowering plants are extremely diverse in their traits related to reproduction, not only the different parts within flowers but also ancillary traits, e.g., inflorescence architecture. A complete understanding of the evolution of these traits requires estimating how selection is operated via different components of female and, especially, male reproductive success.

Again, using Pulsatilla alpina as my research system, I have been studying how different traits, e.g., floral sex allocation, phenology, and morphological traits, affect different components of female (e.g., selfing rate, seed predation, pollination rate...etc.) and male (e.g., siring success, pollen dispersal distance...etc.) reproductive success. By jointly evaluating the selection via the two sex functions, we are able to address questions related to sexual antagonistic selection and the resolution of sexual conflicts to explain the polymorphisms in those traits.

Intra-locus sexual conflict in bisexual flowers

Unisexual male flowers in andromonoecious Pulsatilla alpina likely represent a resolution to sexual conflicts within bisexual flowers. See Chen and Pannell 2023 for more details.

Plant-animal interactions

Plant-animal interactions include not only mutualism but also antagonism. I am interested in understanding how the interactions with different partners may shape the ecology and evolution of flowers.

Selection by antagonists on floral traits

I have been studying the interaction with antagonists such as pre-dispersal seed predators (also parasitoid wasps), florivores, and herbivores in Pulsatilla alpina. I addressed questions such as 1) how do different floral traits affect the interaction with a certain partner? 2) how do the animals forage using different cues? 3) how does that affect the fitness and thus the selection?

Pollination ecology of alpine plants in subtropical Taiwan

The alpine ecosystem and flora in subtropical Taiwan possess a huge number of endemic species as a result of migration and vicariance during the ice age. However, the general ecology of these alpine plants is not well understood.

I have been involved in projects to study the pollination ecology of the alpine plants in Taiwan since 2017 in collaboration with Prof. Gaku Kudo (Hokkaido University) and Prof. Chun-Neng Wang (Nation Taiwan University).

Natural history of pollination ecology

One of my research interests is to describe the pollination ecology of the flora of Taiwan. I have studied the generalized bird pollination in Aeschynanthus acuminatus and the fungus gnat pollination in Euonymus laxiflorus (in collaboration with Dr. Ko Mochizuki). My goal is to document the biodiversity and share the findings with the general public.