Reproductive Output and Insect Behavior in Hybrids and Apomicts from Limonium ovalifolium and L. binervosum Complexes (Plumbaginaceae) in an Open Cross-Pollination Experiment

Abstract

Ex situ plant collections established from seeds of natural populations are key tools for understanding mating systems of intricate taxonomic complexes, as in the Limonium Mill. genus (sea lavenders, Plumbaginaceae). Plants show a polymorphic sexual system associated to flower polymorphisms such as ancillary pollen and stigma and/or heterostyly that prevents self and intramorph mating. The main objectives of this study were to investigate the significance of pollen-stigma dimorphisms and the role of flower visitors in the reproductive output of hybrids arising from sexual diploids of Limonium ovalifolium complex and apomicts tetraploids of L. binervosum complex in an open cross-pollination experiment. Results showed that, similarly to parental plants, hybrids present inflorescence types, self-incompatible flowers, and produced regular pollen grains with the typical exine patterns, with medium to high viability. By contrast, apomicts show floral polymorphisms, inflorescences, and pollen grains of maternal phenotype but with low stainability. Several insects’ species visited the inflorescences of parental plants and both hybrids and apomicts and some of these insects carried A and/or B pollen grains on their bodies, especially Clepsis coriacana (Rebel) and Tapinoma sp. Insects’ floral visits to hybrids and apomicts seem to be independent of pollen fertility and plants’ reproductive modes. Both hybrids and apomicts were able to produce fertile seeds, although the latter showed more seedlings with developmental anomalies than the first plants. The findings demonstrate that there is a weak reproductive barrier between the diploid species of L. ovalifolium complex as they can hybridize and produce fertile hybrids, provided there is pollen transport by pollinator insects. This study supports that apomixis is a strong reproductive barrier between both L. ovalifolium and L. binervosum complexes but did not allow us to exclude reproductive interferences of apomict pollen into sexuals.

Pollination Contribution Differs among Insects Visiting Cardiocrinum cordatum Flowers

“…Species visits were classified either as (1) those that entered the flower (i.e., those that arrived at the adaxial surface of the corolla) or (2) those that did not enter the flower (i.e., those that arrived only at the external (abaxial) surface of the corolla). Whenever possible, each individual flower-visiting species was captured into either a vial (5,15, or 20 mL) or a plastic bag (Ziploc, Asahi Kasei, Tokyo, Japan), depending on the body size. Some visitors were recorded as described but were not successfully captured.…”

“…We calculated fruit set (i.e., fruit-to-flower ratio [51,52]) and the seed number per fruit for the 85 bagged fruits used for the pollinator exclusion experiment and, additionally, for different 84 uncovered flowers (i.e., open pollination treatment [15,18,29]) from 15 individuals in the same population. The bags were removed when the flowering period was complete.…”

“…The maintenance of genetic diversity is important for the conservation of wild plant species, and successful cross-pollination plays a major role in gene flow to maintain the genetic diversity of plant populations [1][2][3][4][5][6][7][8][9], especially when a population is fragmented [5][6][7][8][9][10]. Additionally, pollination is a central issue in studies on plant-animal interactions [11][12][13][14][15], plant reproductive biology [15][16][17][18][19][20], and on improvement of agricultural production [15,[20][21][22][23][24][25][26][27][28]. For animal-pollinated flowers, pollination effectiveness differs among visitors of different species [3,5,[12][13][14][15]19,29].…”

“…Additionally, pollination is a central issue in studies on plant-animal interactions [11][12][13][14][15], plant reproductive biology [15][16][17][18][19][20], and on improvement of agricultural production [15,[20][21][22][23][24][25][26][27][28]. For animal-pollinated flowers, pollination effectiveness differs among visitors of different species [3,5,[12][13][14][15]19,29]. Some visitors obtain pollen or nectar from flowers without contributing as pollinators for some plant species, phenomena known as pollen or nectar theft [30], or nectar robbing for cases where a visitor damages a flower [31].…”

Ovule Transcriptome Analysis Discloses Deregulation of Genes and Pathways in Sexual and Apomictic Limonium Species (Plumbaginaceae)

“…The genus comprises c. 350 species with sexual and apomixis reproductive modes [ 25 ], having triploid and tetraploid apomicts with very large distributions in the Mediterranean region and the Atlantic coast [ 26 , 27 , 28 ]. The mode of speciation in the genus has been hypothesized to combine a polymorphic sexual system, hybridization under alloploid conditions, polyploidy combining autoploidy (unreduced pollen), allopolyploidy, and apomixis [ 13 , 24 , 25 , 29 , 30 , 31 ]. The polymorphic sexual system is associated with flower polymorphisms (ancillary pollen and stigma and/or heterostyly) and self-incompatibility (SI) under sporophytic control [ 29 , 30 ].…”