Summer Heatwave Impacts on the European Kelp Saccharina latissima Across Its Latitudinal Distribution Gradient

Kelps are important foundation species in coastal ecosystems currently experiencing pronounced shifts in their distribution patterns caused by ocean warming. While some populations found at species’ warm distribution edges have been recently observed to decline, expansions of some species have been recorded at their cold distribution edges. Reduced population resilience can contribute to kelp habitat loss, hence, understanding intraspecific variations in physiological responses across a species’ latitudinal distribution is crucial for its conservation. To investigate potential local responses of the broadly distributed kelp Saccharina latissima to marine heatwaves in summer, we collected sporophytes from five locations in Europe (Spitsbergen, Bodø, Bergen, Helgoland, Locmariaquer), including populations exposed to the coldest and warmest local temperature regimes. Meristematic tissue from sporophytes was subjected to increasing temperatures of Δ+2, Δ+4 and Δ+6°C above the respective mean summer temperatures (control, Δ±0°C) characteristic for each site. Survival and corresponding physiological and biochemical traits were analyzed. Vitality (optimum quantum yield, Fv/Fm) and growth were monitored over time and biochemical responses were measured at the end of the experiment. Growth was highest in northern and lowest in southern populations. Overall, northern populations from Spitsbergen, Bodø and Bergen were largely unaffected by increasing summer temperatures up to Δ+6°C. Conversely, sporophytes from Helgoland and Locmariaquer were markedly stressed at Δ+6°C: occurrence of tissue necrosis, reduced Fv/Fm, and a significantly elevated de-epoxidation state of the xanthophyll cycle (DPS). The variations in phlorotannins, mannitol and tissue C and N contents were independent of temperature treatments and latitudinal distribution pattern. Pronounced site-specific variability in response to increasing temperatures implies that exceeding a threshold above the mean summer temperature exclusively affect rear-edge (southernmost) populations.

Characterisation of seed dormancy of 12 Chilean species of Nolana (Solanaceae) from the coastal Atacama Desert

The genus Nolana (Solanaceae) comprises numerous species endemic to the coastal Atacama Desert of Chile and Peru of high ornamental potential and conservation value. The environments in which these species have evolved and are present today correspond to particular conditions in the midst of a hyper-arid habitat, so the study of their germination requirements and characterisation of seed dormancy becomes important in terms of conservation but also for ecological and evolutionary purposes. Different treatments were performed on mericarps of 12 species of Nolana: control (intact seeds imbibed in distilled water), scarification in funicular plug and distilled water and scarification in funicular plug and addition of GA3 (500 ppm); their permeability to water was also tested. It was determined that the species did not present physical dormancy, as had been previously reported, but rather physiological dormancy (PD). Germination results after treatments were not homogeneous among all 12 species, indicating differences in their dormancy levels. Also, the important role of the endosperm in the prevention of germination for the studied Nolana species was highlighted. Regarding the relationship between the level of PD (expressed as the percentage of germination for the most successful treatment) and the latitudinal distribution of the species or their phylogenetic closeness, it was determined that, for the studied species, their proximity in terms of clades was more relevant than their latitudinal distribution.

The advertisement call of Gastrotheca chrysosticta Laurent, 1976 (Anura: Hemiphractidae)

The genus Gastrotheca Fitzinger, 1843 currently harbors 75 species (Frost 2020). These marsupial frogs have a broad latitudinal distribution range in Central and South America, from Costa Rica southward to Argentina (Duellman 2015). The advertisement call features as the pulse structure, call duration, and repetition pulse rate are used by researchers to recognize the species of Gastrotheca (Duellman 2015). The availability of call descriptions is also crucial for recognizing these species with secretive life habits and implementing long-term passive acoustic monitoring programs (Vaira et al. 2011; Akmentins et al. 2014).