Clonality is evolutionarily flexible, yet it arises through contrasting developmental pathways that are not necessarily mutually exclusive within species and differ in whether plants form adventitious shoots on roots or adventitious roots on horizontal stems. Here, we suggest that auxin-cytokinin balance offers a comparative interspecific perspective on these alternative pathways. This idea builds on a classical principle from tissue-culture studies, in which relative auxin-cytokinin balance influences whether root or shoot developmental programmes are expressed. We extend this logic from local organogenesis to naturally occurring clonal architectures, asking whether root-derived and stem-derived clonality are associated with contrasting hormonal settings. A comparative dataset of 20 Central European herbaceous species is consistent with this view. Root-derived clonality was associated with lower auxin content and lower auxin/cytokinin ratios, whereas stem-derived clonality showed higher values, with non-clonal species occupying intermediate positions. Importantly, these measurements were obtained from young plants before clonal organs were fully developed, indicating that the observed pattern characterises an early ontogenetic stage rather than the hormonal state of mature clonal organs. Whether these associations persist or change during clonal-organ development remains unresolved. We do not present this pattern as a general explanation for why particular clonal growth forms evolve. Instead, we propose that comparative hormone profiling may help link developmental regulation, clonal architecture and whole-plant ecological strategy, and provide a basis for examining how these relationships vary across ontogeny.
Insular plants that are currently little browsed by ungulates may face increased damage if herbivore pressure rises and alternative forage becomes scarce. Understanding their responses to tissue loss is therefore relevant even when browsing is rarely observed. We investigated current goat browsing and responses to simulated herbivory in Hypericum balearicum L., a shrub endemic to the Balearic Islands. We combined a field experiment, monitoring exposed and individually fenced plants at two sites biweekly for one year, with an ex situ clipping experiment involving three treatments: no clipping, 50% and 75% aboveground biomass removal. Three months after clipping, we assessed survival, flowering, biomass, leaf traits, physiological performance and leaf chemistry. In the field, no signs of goat browsing were observed during the year of monitoring. In the clipping experiment, plants resprouted, and survival did not differ significantly among treatments. However, final shoot and root biomass were lower than in controls, and flowering was markedly reduced, with no flowers recorded after severe clipping. Physiological responses included increased chlorophyll content and maximum photochemical efficiency of photosystem II, while mass-based net photosynthesis remained unchanged. Severe clipping also increased specific leaf area, electron transport rate and lipid peroxidation, and clipping altered foliar secondary metabolite composition. These findings show that the absence of observed browsing under current field conditions coexists with a capacity for vegetative recovery after tissue loss, but recovery was accompanied by reduced biomass and flowering over the study period. Although future goat consumption remains untested, our results indicate that substantial damage could impose growth and reproductive costs on this currently little-browsed endemic shrub.
Marcescent litter decomposition, in which dead leaves remain attached to the plant and decay in situ before reaching the soil surface, is a crucial ecological process that influences nutrient cycling and carbon dynamics. However, the differences between marcescent litter decomposition and soil surface decomposition, as well as the effects of these processes on subsequent soil surface decomposition, remain insufficiently understood. This study focused on Lindera glauca Blume, a species that retains most of its leaves through the winter after senescence until the subsequent growing season. This study aimed to compare the decomposition rates and nutrient dynamics of L. glauca litter during the marcescent phase versus soil surface decomposition, and to examine how these prior decomposition conditions affect subsequent soil surface decomposition. Results showed that the mass loss during marcescent phase was approximately 2.75 times that of soil surface decomposition, driven primarily by abiotic factors such as solar radiation and precipitation. During the subsequent soil surface decomposition phase, mass loss of litter with prior marcescent decomposition was approximately 1.65 times that of litter previously decomposed on the soil surface. This indicates a positive legacy effect, whereby changes in litter properties during the marcescent phase accelerated subsequent decomposition on the soil surface. Our findings highlight the ecological importance of marcescent litter decomposition and suggest that this process may need to be considered when evaluating nutrient cycling and carbon storage in forests with marcescent species.
Recent studies of widespread Eurasian steppe biota have uncovered previously unexpected genetic divergence between populations from edaphic, extrazonal European steppes and their relatives thriving in the vast, zonal steppe belt. For instance, different genetic lineages – partly corresponding to differences in ploidy – were previously identified in Astragalus onobrychis L. (Fabaceae), but the sampling for morphometric analyses was insufficient for taxonomic conclusions. Hence, we strongly increased the sampling effort for both morphometric and genomic analyses to investigate evolutionary origin and differentiation of Alpine and Apennine populations of A. onobrychis using an integrative approach. Our study combined analyses of restriction site associated DNA sequencing, relative genome size estimation, and multivariate morphometric analyses. After establishing the genetic and morphological divergence of the aforementioned populations, we described them as two new species, Astragalus vallium-aridarum E. Huber, Maylandt & Schönsw., sp. nov. endemic to the Alps and Astragalus italicus E. Huber, Maylandt & Schönsw., sp. nov. endemic to the southeastern Alps and the Northern and Central Apennines. We demonstrate that A. vallium-aridarum is a hybrid species originating from cross-ploidy hybridisation between octoploid A. onobrychis and tetraploid A. italicus. We provide diagnoses, descriptions, geographical distributions, and conservation status of these enigmatic elements of extrazonal steppes along with a determination key for the Alpine, Apennine and Pannonian species of the A. onobrychis species group.
Reciprocal interactions between plants and their local environment, commonly referred to as ‘plant-soil feedback’ (PSF), have been a focal component of plant population and community ecology over the past two decades. Non-native, perennial forage grasses can have tremendous effects on abiotic properties and biotic communities of native ecosystems; however, very few studies have explored PSF between native and non-native perennial prairie grasses, and how PSF between the two are affected by biomass removal. Here, we present a standard two-phase PSF experiment conducted in a greenhouse, pairing one non-native and one native grass of both C3 and C4 photosynthetic pathways. Plant–soil feedback was measured through plant productivity, arbuscular mycorrhizal (AM) fungal colonization, and neutral lipid fatty acids (NLFAs). Defoliation generally neutralized PSF, regardless of whether the PSF was being measured through biomass production, intra-radical AM fungal colonization, or NLFAs. Second, responses of AM fungi to defoliation, conditioning species, and feedback species were complex, with significant two- and three-way interactions for cool- and warm-season pairings, respectively. Both cool- and warm-season grass pairs displayed strong positive PSF for AM fungal colonization, though intra-radical colonization in the two functional groups was differentially affected by defoliation. Through alterations to abundance, and perhaps even composition, of soil microbial communities, defoliation was demonstrated to neutralize, and even completely shift direction of, PSFs between native and non-native grasses. Overall, these results highlight the differential effects of defoliation on plant productivity and AM fungal abundances of native and non-native cool- and warm-season grasses, and how these alterations influence PSF dynamics between these often-interacting grass species, thus shedding light onto complex coexistence dynamics.
