The reproductive strategy of a pollinator-limited Himalayan plant, Incarvillea mairei(Bignoniaceae)

Abstract

BackgroundPlants may adapt to alpine habitats by specialization in the reproductive strategy and functional aspects of their flowers and pollination systems. Alpine habitats reduce the opportunities for cross-pollination in a relatively high proportion of alpine plant species, and self-pollination may be favored in these adverse conditions. Here, we investigated the mating system and pollination of Incarvillea mairei, a perennial Himalayan herb typically found at altitudes between 3000 and 4500 m.ResultsAnalyses of floral morphology, observation of plant-pollinator interactions, and hand pollination experiments were conducted in three natural populations. Outcrossing rates and effective numbers of pollen donors were assessed in 45 open-pollinated families by using progeny analysis based on seven microsatellite markers. Incarvillea mairei displayed a set of apparently specialized floral traits, the stigma is sensitive to touch and close immediately and its reopening allows a second opportunity for the receipt of pollen. The species is fully self-compatible but employs a predominantly outcrossing mating system according to parentage analysis (tm > 0.9). Fruit set was low (26.3%), whereas seed set was high (67.2%), indicating that this species suffers pollinator limitation. Its main effective pollinator was Halictus sp., and visitation frequency was low.ConclusionsFloral features such as having a sensitive stigma and anther-prongs, in conjunction with pollinator behavior, function together contributing to a set of unique reproductive adaptations that enhance outcrossing success. The increased floral longevity and high pollination efficiency operated as compensatory mechanisms to counteract low pollinator visitation frequency.

Ovule bet‐hedging at high elevation in the South American Andes: Evidence from a phylogenetically controlled multispecies study

“…In several strongly outcrossing high Andean species, less reliable visitation on higher sites is known to be ameliorated by intrinsically long‐lived flowers of capitula in Asteraceae or more prolonged flower longevity produced by the plastic extension of the flower life span under cooler temperatures and higher soil moisture content allowing more time for the accumulation of scarce pollinator visits (Arroyo et al, ; Arroyo, Dudley, Jespersen, Pacheco, & Cavieres, ; Dudley, Arroyo, & Fernández‐Murillo, ; Medan, ; Pacheco, Dudley, Cabezas, Cavieres, & Arroyo, ; Torres‐Díaz et al, ). Long‐lived flowers have also been implicated in compensating low and stochastic visitation in several other alpine areas (Ai et al, ; Bingham & Orthner, ; Duan, & Liu, ; Pickering, ; Steinacher & Wagner, ; Utelli & Roy, ). However, in the Andes, flower longevity compensation is rarely fail‐safe as evidenced by significant pollen limitation in most strongly outcrossing species studied to date with supplemental pollination and higher levels of pollen limitation in upper elevation populations of individual species (Arroyo et al, ; Ladd & Arroyo, ; Muñoz & Arroyo, ; Muñoz & Cavieres, ; Torres‐Díaz et al, ).…”

“…Acceptance of ovule bet-hedging as deeply engrained in flowering plants would be greatly strengthened by empirical evidence coming from comparisons of ovule number in plant communities differing in levels of pollination stochasticity. In general, alpine and Arctic habitats are characterized by strongly stochastic pollination as evidenced by variable visitation rates, erratic visitation, wide variation in numbers of pollen grains deposited on stigmas, and large differences in seed set per flower (Ai, Zhou, Xu, Wang, & Li, 2013;Bergman et al, 1996;Eriksen, Molau, & Svensson, 1993;Fulkerson, Whittall, & Carlson, 2012;Hocking, 1968;Kasagi & Kudo, 2003;Kudo, Hirao, & Kawai, 2011;Ladinig & Wagner, 2007;Ladinig, Hacker, Neuner, & Wagner, 2013;Lundemo & Totland, 2007;McCall & Primack, 1992;Tiusanen, Hebert, Schmidt, & Roslin, 2016;Torres-Diaz et al, 2007;Totland, 1994Totland, , 1997Tur, Sáez, Traveset, & Aizen, 2016;Waites & Ågren, 2004). Progressively shorter growing seasons with increasing elevation and latitude place further restrictions on pollination and seed set by limiting the amount of time available for flowering and seed maturation (Körner, 2003).…”

Pollen limitation is not the rule in nival plants: A study from the European Central Alps

“…Pollen limitation is thought to be a general phenomenon under the harsh climatic conditions at high latitudes and elevations. A number of studies in the alpine tundra of northern Europe (Elberling, 2001; Totland and Sottocornola, 2001; Totland and Schulte‐Herbrüggen, 2003), the European Central Alps (Gugerli, 1998), the Himalayas (Ai et al, 2013), the mountains of North America (Galen, 1985; Shykoff, 1988; Campbell and Halama, 1993), the Chilean high Andes (Muñoz and Arroyo, 2006), and the mountains of northern Japan (Kudo and Suzuki, 2002; Kasagi and Kudo, 2003) and Alaska (Fulkerson et al, 2012) support this assertion. Pollen limitation has also been reported for the subarctic (Stenström and Molau, 1992) and the arctic (Philipp et al, 1996).…”

Reproductive Biology of T. chinensis and T. ramosissima (Tamaricaceae: Theineae) from Gansu, Northwestern China

“…Reproductive success in variable environments in which pollination may be uncertain is a common problem that confronts many plants (Ai et al, 2013). Pollination is a key process as the first stage in sexual reproduction of plants, and an essential prerequisite for the development of fruits and seeds (Kevan et al, 1990).…”

“…Therefore, pollination affects a variety of ecological and evolutionary processes of many plant species, such as floral attraction, plant mating system and population persistence (Bond, 1994;Kearns et al, 1998;Ashman et al, 2004;Ashman & Morgan, 2004). During the short growing seasons, harsh weather and low densities of pollinators could affect the effective pollination (Ai et al, 2013;Ashman et al, 2004). Studying reproductive biology is helpful to understanding of pollination success, as well as natural factors influencing dynamics of populations (Arias-Cóyotl et al, 2006).…”