Plant Ecology

Aikins, Timothy K.; Thomson, Robert L.; Cramer, Michael D.

doi: 10.1007/s11258-023-01333-1pmid: N/A

Islands of fertility associated with tree/shrub patches in arid grasslands create spatial heterogeneity of soil nutrients. Faunal activities under these trees/shrubs may contribute to diverse characteristics of these fertile patches of soil due to different faecal inputs. This study used the tree islands of fertility (TIFs) created by camelthorn (Vachellia erioloba) and shepherd trees (Boscia albitrunca) and these species that also host sociable weavers (Philetairus socius) nests (bird islands of fertility; BIFs) in the Kalahari Desert to investigate the diversity in islands of fertility. We hypothesized that grasslands, the TIFs, and the BIFs differ in both the concentrations and stoichiometries of soil nutrients due to the sources of nutrients and that this subsequently determines the growth and foliar nutrient concentrations and stoichiometries of plants that grow on these soils. We predicted that seedlings grown on soils from BIFs would have greater growth, higher biomass yield, and higher foliar nutrients than those grown on soils from TIFs and grasslands. We sampled and grew camelthorn seedlings in soils from BIFs, TIFs, and matrix grasslands. Despite the higher soil nutrients in TIFs than in grasslands, there were no significant differences in seedling growth. However, we observed significantly higher seedling growth in BIF soils compared to TIF soils. Seedlings grown in soils from BIFs and grasslands allocated more growth to shoots and roots, respectively, while those grown on TIF soils were intermediate. The foliar nutrient stoichiometries of seedlings grown in BIF soils were similar to the stoichiometric ratios in BIF soils and in sociable weaver faecal matter. This shows that the faecal input of the sociable weaver accounts for the growth differences in these islands of fertility. The ecological engineering activities of the sociable weaver address nutrient limitations for camelthorn seedling growth, which TIF soils could not address despite the high faecal input of mammals.

Li, Yu-Lin; Xiong, Yun-Tao; Jin, Jie-Ren; Wang, Chao-Nan; Pan, Zhi-Li; Wang, Jie; Wang, Yan; Wang, Yi

doi: 10.1007/s11258-023-01335-zpmid: N/A

Successful germination and establishment of invasive plants is a key early step during their invasion, which influences their invasive potential. Previous studies have focused on the differences in traits between native and invasive plants, but little is currently known regarding the evolutionary changes in seeds when invasive plants were reintroduced into their homeland. We planted the seeds (F1) of 13 Triadica sebifera populations invading the USA into their native habitat (31° 45′ N, 114° 39′ E, Dawu, China) in 2014. After F1 matured (2019), we collected their seeds (F2) and the seeds of 30 native populations to test the differences in physical and chemical properties, seed hormones, and germination traits between the seeds of reintroduced and native T. sebifera populations. We found that the seeds of reintroduced populations of T. sebifera have thinner wax coating and significantly higher ABA, GA19, GA24, and GA53 hormone contents than the native populations. In addition, the seeds of native populations of T. sebifera have thicker wax coating and significantly higher ACC and GA1 hormone contents and higher ratio of TGA:ABA than the reintroduced populations. However, we detected no significant differences in all other seed traits assessed, including physical and chemical properties as well as germination traits. In summary, these results indicate that most seed traits of these invasive plants either show phenotypic plasticity or simply did not change in their invasive range, which offers us with a new perspective to understand the invasion mechanisms of plants reproducing by seeds.

Lima, Ayslan Trindade; Meiado, Marcos Vinicius

doi: 10.1007/s11258-023-01336-ypmid: N/A

In seasonally dry tropical forests, seeds are naturally submitted to hydration and dehydration cycles (HD cycles) during germination, which can promote the seed hydration memory expression. We investigated how seeds of Pilosocereus catingicola subsp. salvadorensis from the same population produced and dispersed in different seasons of the year express seed hydration memory under water deficit after discontinuous hydration, at different hydration times. We collected seeds produced during the dry season and dispersed at the beginning of the rainy season and seeds produced during the rainy season and dispersed at the beginning of the dry season. Seeds were submitted to 0, 1, 2 and 3 HD cycles with different hydration times and placed to germinate under optimal temperature and light conditions. After verifying that the hydration time between cycles did not influence germination response of the studied species, seeds collected in both seasons were submitted to 0, 1, 2 and 3 HD cycles and placed to germinate at different osmotic potentials (0.0, − 0.1, − 0.3, − 0.6, and − 0.9 MPa). After evaluating the germination parameters, we observed that (1) seeds from the same population, produced and dispersed in different seasons, express seed hydration memory in a different way during their germination process and (2) discontinuous hydration confers greater acquisition of tolerance to seeds produced during dry season. Such germination responses to HD cycles characterize the seed hydration memory expression, which is influenced by the environmental conditions present during seed development and post-dispersion, conferring ecological implications on the reproductive success of the species.

Reiter, Noushka; Wicks, Mike; Pollard, Gail; Brown, Graham; Menz, Myles; Bohman, Björn

doi: 10.1007/s11258-023-01334-0pmid: N/A

Critical for conserving endangered orchids is identifying their pollinators and their distribution. Caladenia xanthochila is an endangered orchid that has floral traits characteristic of pollination by food foraging insects. We identified the pollinator(s), mechanisms of attraction and the presence of pollinators at natural, existing and potential translocation sites. Furthermore, we quantified pollination success at translocation sites and investigated the effect of rainfall on pollination success over 19 years at a natural site. We clarify if sharing of pollinators occurs with closely related species by comparing the CO1 barcoding region of the pollinators' DNA. Caladenia xanthochila was pollinated by a single species of thynnine wasp, Phymatothynnus aff. nitidus. Caladenia xanthochila produced 27.0 µg ± 7.1 sucrose on the labellum, while pollinators vigorously copulated with glandular clubs on the sepal tips, suggestive of a mixed pollination system. Pollination success of C. xanthochila was 7.6 ± 1.5% SE at the natural site and 16.1 ± 3.6% SE across the translocation sites. Furthermore, hand pollinations demonstrated that pollination was pollen limited. Pollination success was significantly related to average rainfall during the growth phase of the orchid (P < 0.001). Potential translocation sites for C. xanthochila were limited, with four of six surveyed lacking the pollinator. We found evidence for cryptic species of Phymatothynnus, with C. xanthochila pollinators being unique amongst the orchids studied. We recommend hand pollinations at translocated and remnant wild populations to boost initial recruitment. The evidence for cryptic species of pollinators further highlights the need for accurate identification of pollinators.

Beck, Jared J.; Richards, Jeannine H.

doi: 10.1007/s11258-023-01337-xpmid: N/A

Functional traits influence plant distributions along broad environmental gradients leading species to occupy communities where their traits enable them to successfully establish and compete for resources. Trait differences are also expected to influence plant distributions and diversity at finer spatial scales within communities. However, relatively few empirical studies have examined the extent to which interspecific trait variation predicts local species-environment distributions. We surveyed herbaceous plants within a heterogeneous acid bedrock glade in south-central Wisconsin to elucidate how traits influence local plant distributions and diversity. Using quadrat-scale environmental covariates (soil depth, canopy openness, and neighborhood tree phenology) and species functional trait means (SLA, vegetative height, and seed mass), we modeled variation in local species distributions as well as plant diversity across 361 quadrats distributed evenly in a 1 ha study plot. Functional traits predictably mediated individualistic species distributions along local gradients in soil depth and canopy openness as well as differential plant responses to variation in canopy leaf phenology. Small-seeded herbs occurred in shallow soil microsites while the prevalence of large-statured plants increased with canopy openness. Local species richness and functional trait dispersion were greatest in microsites near canopy gaps where sun-adapted and shade-adapted plant species co-occur and in microsites surrounded by later-leafing trees. Interspecific trait differences influence local species distributions and shape spatial patterns of diversity within heterogeneous plant communities like bedrock glades. The parallels between local plant distributions within this heterogeneous community and regional plant distributions across the landscape suggest trait-mediated ecological sorting influences plant distributions along environmental gradients similarly across spatial scales.