High herkogamy but low reciprocity characterizes isoplethic populations of Jasminum malabaricum, a species with stigma‐height dimorphism

Abstract

• Studies of floral polymorphisms have focused on heterostyly, while stigma-height dimorphism has received considerably less attention. Few studies have examined the reproductive biology of species with stigma-height dimorphism to understand how factors influencing mate availability and pollen transfer are related to morph ratios in populations. • Floral morphological traits, especially herkogamy and reciprocity, pollinator visitation, breeding system and spatiotemporal mate availability, are known to affect intermorph pollination and morph ratios in species with stigma-height dimorphism. In this study, we investigated the presence of stigma-height dimorphism and estimated morph ratios in four naturally occurring populations of Jasminum malabaricum. We quantified morph-and population-specific differences in the abovementioned factors in these populations to understand the observed morph ratios. • The positions of anthers and stigmas were characteristic of stigma-height dimorphism, the first report of this polymorphism in the genus. All study populations were isoplethic, implying equal fitness of both morphs. Herkogamy was higher in the shortstyled morph, while reciprocity was higher between the long-styled stigma and shortstyled anthers. Long-and short-tongued pollinators were common floral visitors, and we observed no differences between morphs in spatiotemporal mate availability or pollinator visitation. Neither morph exhibited self-or heteromorphic incompatibility. • The short-styled stigma had lower reciprocity but likely receives sufficient inter-morph pollen from long-tongued pollinators, and also by avoiding self-pollination due to higher herkogamy. These results highlight the importance of sufficient effective pollinators and floral morphological features, particularly herkogamy, in maintaining isoplethy in species with stigma-height dimorphism.

Herkogamy but not reciprocity is a better predictor of legitimate pollen transfer and fruit set inJasminum malabaricum, a self-compatible species with stigma-height dimorphism

“…Pollen transfer and reproductive success can be influenced by morph specific differences in various factors affecting mating opportunities. In all four study populations, the short-styled morph had higher herkogamy, while reciprocity was higher between the long-styled stigmas and the short-styled anthers (Ganguly and Barua 2020). With the exception of these two traits, morphs did not differ in spatiotemporal mate availability, pollinator visitation, and did not exhibit physiological incompatibility (Ganguly and Barua 2020).…”

“…In all four study populations, the short-styled morph had higher herkogamy, while reciprocity was higher between the long-styled stigmas and the short-styled anthers (Ganguly and Barua 2020). With the exception of these two traits, morphs did not differ in spatiotemporal mate availability, pollinator visitation, and did not exhibit physiological incompatibility (Ganguly and Barua 2020). Since the mating opportunities were similar for both morphs it is unlikely to be a confounding factor in our investigations.…”

“…Since the mating opportunities were similar for both morphs it is unlikely to be a confounding factor in our investigations. The species exhibits pollen size dimorphism (Ganguly and Barua 2020) which is rare in species with stigma-height dimorphism.…”

“…As reported in a previous study (Ganguly and Barua 2020), one flower from 30 individuals of each morph was collected from Bhimashankar, Mulshi and Kaas, between March and April of 2015 and 2017, and preserved in formalin acetic alcohol (FAA; 2.5%:2.5%:95%). In Trimbak, one flower was collected from 20 long-, and 19 short-styled individuals because of the small population size and limited availability of individuals.…”

“…In this study, we examined the variation in reciprocity and herkogamy among individuals of four naturally occurring isoplethic populations of J. malabaricum (Ganguly and Barua 2020) with stigma-height dimorphism. We estimated reciprocity for an individual as the average mismatch between the stigma of that individual and the anthers of all other individuals of the complementary morph.…”