Although phenotypic plasticity can be advantageous in fluctuating environments, it may come too late if the environment changes fast. Complementary chromatic adaptation is a colorful form of phenotypic plasticity, where cyanobacteria tune their pigmentation to the prevailing light spectrum. Here, we study the timescale of chromatic adaptation and its impact on competition among phytoplankton species exposed to fluctuating light colors. We parameterized a resource competition model using monoculture experiments with green and red picocyanobacteria and the cyanobacterium Pseudanabaena, which can change its color within ∼7 days by chromatic adaptation. The model predictions were tested in competition experiments, where the incident light color switched between red and green at different frequencies (slow, intermediate, and fast). Pseudanabaena (the flexible phenotype) competitively excluded the green and red picocyanobacteria in all competition experiments. Strikingly, the rate of competitive exclusion was much faster when the flexible phenotype had sufficient time to fully adjust its pigmentation. Thus, the flexible phenotype benefited from its phenotypic plasticity if fluctuations in light color were relatively slow, corresponding to slow mixing processes or infrequent storms in their natural habitat. This shows that the timescale of phenotypic plasticity plays a key role during species interactions in fluctuating environments.Keywords: adaptive dynamics, cyanobacteria, phycocyanin, phycoerythrin, resource competition theory, Synechococcus.Fluctuations in environmental conditions pose serious challenges to organisms. Many organisms respond to environmental changes by physiological and morphological adaptations. This flexible strategy, known as phenotypic plasticity, may improve their fitness in the new environments (Agrawal 2001). For example, plants increase their leaf area during periods of reduced light (Sultan and Bazzaz 1993), cladocerans develop armored helmets in the presence of predators (Woltereck 1909;Laforsch and Tollrian 2004), and some green algae aggregate into colonies to reduce their edibility for grazers (Hessen and Van Donk 1993;Lampert et al. 1994).Intuitively, phenotypic plasticity seems a suitable strategy to cope with environmental fluctuations. However, adaptation takes time. If adaptation is too slow, organisms will not be able to keep up with changes in their environment, resulting in a permanent mismatch between the physiology of the organisms and their environmental conditions. Indeed, theory shows that adaptation can even be disadvantageous when it has a strong time delay (Padilla and Adolph 1996;Gabriel 2005). Yet, although many studies have investigated phenotypic plasticity in fluctuating environments (e.g., Chesson et al. 2004;Egas et al. 2004;Abrams 2006aAbrams , 2006bGélinas et al. 2007; Van der Stap et al. 2007), the timescale of phenotypic adaptation has received surprisingly little attention (Miner et al. 2005).The colorful process of complementary chromatic ad-E170 ...

Cryptococcus neoformans and Cryptococcus gattii are yeasts that cause meningoencephalitis, but that differ in host range and geographical distribution. Cryptococcus neoformans occurs world-wide and mostly infects immunocompromised patients, whereas C. gattii occurs mainly in (sub)tropical regions and infects healthy individuals. Anomalous C. neoformans strains were isolated from patients. These strains were found to be monokaryotic, and diploid or aneuploid. Amplified Fragment Length Polymorphism (AFLP) and sequence analyses indicated that AFLP genotypes 2 (C. neoformans) and 4 (C. gattii) were present. The strains were serologically BD. Mating- and serotype-specific PCR reactions showed that the strains were MATa-serotype D/MATalpha-serotype B. This study is the first to describe naturally occurring hybrids between C. neoformans and C. gattii.

In this study, we show that natural phototrophic populations can be probed individually for their in situ ␦ 13 C signature by linking fluorescence-activated cell sorting and isotope-ratio mass spectrometry (IRMS) using in-line pyrolytic methylation. This novel methodology greatly improved the resolution in discriminating and tracing the differential carbon (C) pathways at the base of the pelagic food web in the cyanobacteria-dominated Lake Loosdrecht (The Netherlands). Our analysis revealed the co-occurrence of phytoplankton taxa differing by 6-10‰ in ␦ 13 C. Predominant micro-and mesozooplankton species reflected this difference as the result of preferential grazing and/ or selective digestion. Flow cytometric (FCM) retrieval of phytoplankton ␦ 13C signatures, applied in conjunction with 13 C-carbonate labeling, also enabled an assessment of in situ population-specific growth rates. Diatoms and green algae exhibited up to ninefold higher growth rates than those for cyanobacterial species. The coexistence of phytoplankton populations widely differing in ␦ 13 C, standing stock, and turnover time has important implications for the interpretation of C transfer in pelagic food webs. Our approach disclosed a disproportional impact on trophic cascades by numerically minor phototrophs that otherwise would have gone unnoticed. Despite the abundance of cyanobacterial-derived C, the zooplankton largely rely on eukaryotic algae for growth. Rotifers take a central position in passing on this algal C to the cyclopoid copepod populations in the lake. The bosminid-dominated cladoceran population uses both the cyanobacterial-and algal-derived C in approximately equal shares.

Over the past two decades, several fungal outbreaks have occurred, including the high-profile ‘Vancouver Island’ and ‘Pacific Northwest’ outbreaks, caused by Cryptococcus gattii, which has affected hundreds of otherwise healthy humans and animals. Over the same time period, C. gattii was the cause of several additional case clusters at localities outside of the tropical and subtropical climate zones where the species normally occurs. In every case, the causative agent belongs to a previously rare genotype of C. gattii called AFLP6/VGII, but the origin of the outbreak clades remains enigmatic. Here we used phylogenetic and recombination analyses, based on AFLP and multiple MLST datasets, and coalescence gene genealogy to demonstrate that these outbreaks have arisen from a highly-recombining C. gattii population in the native rainforest of Northern Brazil. Thus the modern virulent C. gattii AFLP6/VGII outbreak lineages derived from mating events in South America and then dispersed to temperate regions where they cause serious infections in humans and animals.

Interspecies hybrids of Cryptococcus neoformans and C . gattii have only recently been reported. We describe a novel C. neoformans × C. gattii hybrid strain (serotype AB) that was previously described as C. gattii and that caused a lethal infection in an AIDS patient from Canada.