Levels and profiles of chlorinated and brominated contaminants in Southern Hemisphere humpback whales, Megaptera novaeangliae.

The study documents the levels and profiles of selected contaminants [polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polybrominated diphenyl ethers (PBDEs) and methoxylated PBDEs (MeO-PBDEs)] in blubber biopsy samples collected from humpback whales (Megaptera novaeangliae) in Antarctic Peninsula waters. In addition, we investigated year-to-year and sex-related differences in the bioaccumulation patterns. Except for hexachlorobenzene (HCB), whose concentrations were in the same range as those found in whales from the Northern Hemisphere, levels of all other compounds were lower in Southern Hemisphere whales compared to literature data on animals from the Arctic and subarctic region. The mean contribution to the sum of all anthropogenic organohalogen compounds (ΣOHC) decreased in the following order ΣPCBs (44%)>HCB (31%)>ΣDDXs (13%)>ΣCHLs (4.6%)>ΣHCHs (4.4%)>ΣPBDEs (0.9%). The predominant compounds within each chemical class were: PCBs 153, 149, 101 and 138; p,p'-DDE; γ-HCH; trans-nonachlor; PBDEs 99 and 47. The most dominant MeO-PBDE congener was 6-MeO-BDE 47. As samples were collected during three consecutive summer seasons, year-to-year trends could be assessed indicating a significant decrease from 2000 to 2003 for ΣCHL levels. Higher ΣPBDE concentrations and higher values of the ΣPBDE / ΣMeO-PBDE ratio, as well as higher ratios between the two MeO-BDEs (2'-MeO-BDE 68/6-MeO-BDE 47) were found in females compared to males. Higher ΣMeO-PBDE concentrations and higher values of the ratios between the lower chlorinated and the higher chlorinated PCBs were found in males than in females. In addition, five out of six significant differences found through discriminant function analysis were gender-related. The literature reports both feeding in mid- to low-latitudes and sex-related differences in migration patterns for humpback whales from the Southern Hemisphere, indicating that the hypothesis of dietary differences between males and females cannot be excluded. Nevertheless, additional studies are required for further investigation of this hypothesis.

Spatiotemporal variation of chasmogamy and cleistogamy in a native perennial grass: fecundity, reproductive allocation and allometry.

It is difficult to assess the relative variability or stability of chasmogamous (CH) and cleistogamous (CL) reproduction in perennial herbs with mixed mating because long-term data in natural populations are unavailable. Here, the aim was to quantify and compare spatial (between-habitat) and temporal (among-year) variation in CH and CL reproduction over 5 years in two subpopulations of the native perennial grass Danthonia compressa. This species produces CH spikelets on terminal panicles in early summer, while axillary CL spikelets, including a basal cleistogene, mature into the autumn. Flowering tillers were collected from a sunny woodland edge and an adjacent shady interior habitat for 5 consecutive years (2017-21). Seed set, fecundity, seed mass and biomass allocation were recorded for the two floral types along with tiller vegetative mass. Bivariate line fitting was used for allometric analysis of CH and CL fecundity. Seed set, fecundity, mass per seed and allocation to seeds differed between floral types and showed significant variation between habitats and among years. Seed set and fecundity in CH panicles were greater than that of axillary CL panicles in most years. Tiller mass positively affected axillary CL seed production and mass of the basal cleistogene. Fecundity and allocation among years were more variable for CH compared to CL reproduction. High seed set and fecundity of CH spikelets suggest that pollination does not limit reproduction via chasmogamy. Late maturation of axillary CL spikelets provides additional fecundity, especially in larger plants along sunny woodland edges. The heavy cleistogene at the tiller base could be important to population persistence, analogous to the axillary bud bank of other perennial grasses that are not cleistogamous. The spatiotemporal stability of CL reproduction underscores the ecological significance of cleistogamy to reproductive fitness.

Heterophyllous Shoots of Japanese Larch Trees: The Seasonal and Yearly Variation in CO2 Assimilation Capacity of the Canopy Top with Changing Environment.

Japanese larch (Larix kaempferi = L. leptolepis) is often characterized by its high growth rate with heterophyllous shoots, but the functional differences of heterophyllous shoots still remain unclear. Recently, abrupt high temperature and drought during spring induced high photosynthetic rate via change in leaf morphology of the deciduous habit. In order to reveal the photosynthetic characteristics of both short and long-shoot needles of sunny canopy of the larch trees using a canopy tower, we calculated the seasonal change of gas exchange characters and leaf mass per area (LMA) and foliar nitrogen content (N) of heterophyllous needles: short and long-shoot needles over 3 years. No marked difference in light-saturated photosynthetic rates (Psat) was observed between short and long shoots after leaf maturation to yellowing, although the difference was obvious in a specific year, which only shows that seasonal change in temperature and soil moisture determines the in situ photosynthetic capacity of needles. The large annual and seasonal variations in Psat in both shoots were found to be mainly determined by climatic variations, while shoot types determined the strategy of their photosynthetic N utilization as well as the stomatal regulation.

Interspecific and temporal variation in herbivore responses to hybrid willows.

We studied herbivory of two species of willows (Salix sericea and S. eriocephala) and their interspecific hybrids to test alternative hypotheses concerning the effects of hybridization on plant resistance. Individually marked plants were identified using morphological traits in the field and random amplified polymorphic DNA (RAPD) band analysis was used to verify the genetic status of many parental and hybrid plants. The desities of 12 herbivore species on plants in the field were compared between two parents and their F2-type hybrids. We found about equal support for the additive, dominance, and hybrid susceptibility hypotheses over 4 years. In one year, one species supported the hybrid resistance hypothesis. Guild membership was not a good predictor of similar responses of species to hybrid versus parental plants. There were marked differences in support for particular hypotheses among years for four herbivore species. This study demonstrates the diversity of responses of phytophages in response to interspecific hybridization, and indicates that year-to-year variation in relative resistance of hybrid plants can be important.