Variation in reproductive modes and population genetic structures of a monocarpic perennial herb, Cardiocrinum cordatum, in relation to habitat fragmentation

Abstract

Reproductive systems are recognized as having a profound influence on the extent and structure of genetic variation in plant populations. To investigate the spatiotemporal variation in the reproductive modes (sexual and vegetative reproduction) and population genetic structures of a monocarpic perennial herb, Cardiocrinum cordatum (liliaceae), we selected a variety of habitats (e.g. large forested area including primeval forest, small fragmented secondary forest, and so on) around Sapporo City, Japan. We conducted breeding experiments, monitored the fate and growth of marked individuals for 3 years, and also analyzed the spatiotemporal genetic variation of flowering plants within the populations using allozyme variation. Plants emasculated prior to anthesis produced mature fruits in all populations examined. However, seed production was significantly lower in the small fragmented populations, possibly because of the low availability of pollinators and subsequent pollen limitation. In these fragmented populations, the mature flowering plants tended to be more dependent on vegetative reproduction for their recruitment, because they can only produce flowers once in their lifetime. Genetic diversity using samples from mature flowering plants in each population was lower in the small fragmented populations than in the large populations. In addition, although genotypic compositions in the fragmented populations were more or less similar during the 3 years of the study, the dominant genotypes changed temporally and spatially every year in the large populations. The present study demonstrated that the reproductive features of C. cordatum can be altered in various environmental conditions, such as habitat fragmentation, and these changes considerably affected the population genetic structures and vice versa.

Inter‐populational variation, but no‐annual variation within populations, in terms of reproductive size and genetic structure in a monocarpic perennial herb, Cardiocrinum cordatum var. glehnii

“…Based on a long-term monitoring study, Araki, Shimatani, Nishizawa, Yoshizane, and Ohara (2010) and Ohara et al (2006) reported that flowering can start after the three-leaved rosette stage, and over 70% of five-leaved and sixleaved rosette plants flowered in the next season. In addition, Narumi and Ohara (2018) recently reported a high flowering probability of small rosette individuals found in several populations of C. cordatum var. glehnii (i.e.…”

The role of sexual and vegetative reproduction in the population maintenance of a monocarpic perennial herb,Cardiocrinum cordatumvar.glehnii

“…Larger‐sized individuals had more numerous flowers; at HU‐1 plants had four to 20 flowers per plant and at HU‐2 plants had two to six flowers. In addition, at HU‐2, vegetative offshoot formation occurred with a lower frequency (Narumi & Ohara ). Control (CON): Individuals were left undamaged to determine resource allocation to sexual and vegetative reproduction in natural conditions. Outcross (OUT): Flowers were emasculated prior to anthesis and then hand‐pollinated with pollen collected from distant flowers. This treatment intended plants to use their resources for maximized seed production. Stigma cut (SC): Styles were cut off before anther dehiscence.…”

“…Largersized individuals had more numerous flowers; at HU-1 plants had four to 20 flowers per plant and at HU-2 plants had two to six flowers. In addition, at HU-2, vegetative offshoot formation occurred with a lower frequency (Narumi & Ohara 2018). 1.…”

“…The field experiments and sampling of materials were conducted at the sites of five populations located in Sapporo city and its vicinity, Hokkaido: Hokkaido University-1 (HU-1), Hokkaido University-2 (HU-2), Nopporo Forest Park (NP), the Botanical Garden (BG) and Chitose (CT) (Narumi & Ohara 2018).…”

“…glehnii should have characteristics significant for sexual and vegetative reproduction that are different from polycarpic plants in terms of quality and quantity. In addition, Ohara et al (2006) and Narumi and Ohara (2018) showed that seed production was affected to a great extent by insect-mediated outcrossing, and individual size in the previous year to flowering varied among populations. Therefore, the relative importance of sexual and vegetative reproduction may differ between populations.…”