Arbuscular mycorrhizal fungi (AMF) are highly important for plant communities in dry or seasonally dry ecosystems, such as the South American Mediterranean-type ecosystem (MTE), considered a biodiversity hotspot. While AMF hold potential for sustainable MTE management and conservation, they have been under investigated on this ecosystem and little is known about AMF spore bank dynamics. In this study, we analyzed the effect of physico-chemical soil factors, phytobiont species, and seasonality on the AMF spore soil density in two sclerophyllous forests (Malloa and San Vicente). We sampled soil once per season during 1 year and beneath four representative tree species for each site. The results show a strong season effect at both sites, while physical-chemical parameters differed between sites. At Malloa, clay content and electrical conductivity were positively correlated with spore density, while available phosphorous showed a negative correlation. At San Vicente, clay content and total nitrogen were positively correlated with spore density, while soil organic matter showed a negative effect. Overall, spore number reached a minimum value in winter and higher values during the growing season at both sites. These results indicate a strong regulation of AMF spore density by seasonal climate, while physico-chemical soil properties exert a host-independent but site-specific effect in both forests.

Factors Affecting Arbuscular Mycorrhizal Fungi Spore Density in the Chilean Mediterranean-Type Ecosystem

The establishment and success of polyploids are thought to often be facilitated by ecological niche differentiation from diploids. Unfortunately, most studies compared diploids and polyploids, ignoring variation in ploidy level in polyploids. To fill this gap, we performed a large-scale study of 11,163 samples from 1283 populations of the polyploid perennial geophyte Allium oleraceum with reported mixed-ploidy populations, revealed distribution ranges of cytotypes, assessed their niches and explored the pattern of niche change with increasing ploidy level. Altogether, six ploidy levels (3x–8x) were identified. The most common were pentaploids (53.6%) followed by hexaploids (22.7%) and tetraploids (21.6%). Higher cytotype diversity was found at lower latitudes than at higher latitudes (> 52o N), where only tetraploids and pentaploids occurred. We detected 17.4% of mixed-ploidy populations, usually as a combination of two, rarely of three, cytotypes. The majority of mixed-ploidy populations were found in zones of sympatry of the participating cytotypes, suggesting they have arisen through migration (secondary contact zone). Using coarse-grained variables (climate, soil), we found evidence of both niche expansion and innovation in tetraploids related to triploids, whereas higher ploidy levels showed almost zero niche expansion, but a trend of increased niche unfilling of tetraploids. Niche unfilling in higher ploidy levels was caused by a contraction of niche envelopes towards lower continentality of the climate and resulted in a gradual decrease of niche breadth and a gradual shift in niche optima. Field-recorded data indicated wide habitat breadth of tetraploids and pentaploids, but also a pattern of increasing synanthropy in higher ploidy levels. Wide niche breadth of tetra- and pentaploids might be related to their multiple origins from different environmental conditions, higher “age”, and retained sexuality, which likely preserve their adaptive potential. In contrast, other cytotypes with narrower niches are mostly asexual, probably originating from a limited range of contrasting environments. Persistence of local ploidy mixtures could be enabled by the perenniality of A. oleraceum and its prevalence of vegetative reproduction, facilitating the establishment and decreasing exclusion of minority cytotype due to its reproductive costs. Vegetative reproduction might also significantly accelerate colonisation of new areas, including recolonisation of previously glaciated areas.

/pdf/intricate-distribution-patterns-of-six-cytotypes-of-allium-52jmammdb7.pdf

Intricate Distribution Patterns of Six Cytotypes of Allium oleraceum at a Continental Scale: Niche Expansion and Innovation Followed by Niche Contraction With Increasing Ploidy Level

Genetic similarities versus morphological resemblance: Unraveling a polyploid complex in a Mediterranean biodiversity hotspot.

Polyploidy has played an important evolutionary role in the genus Festuca (Poaceae), and several ploidy levels (ranging from 2n = 2x = 14 to 2n = 12x = 84) have been detected to date. This study aimed to estimate the genome size and ploidy level of two subspecies belonging to the F. yvesii polyploid complex by flow cytometry and chromosome counting. The phenotypic variation of the cytotypes was also explored, based on herbarium material. The genome size of F. yvesii subsp. lagascae has been estimated for the first time. Nuclear 2C DNA content of F. yvesii subsp. summilusitana ranged from 21.44 to 31.91 pg, while that of F. yvesii subsp. lagascae was from 13.60 to 22.31 pg. We report the highest ploidy level detected for Festuca (2n = 14x = 98) and previously unknown cytotypes. A positive correlation between holoploid genome size and chromosome number counts shown herein was confirmed. The morphometric approach showed a slight trend towards an increase in the size of some organs consistent with the variation in the ploidy level. Differences in characters were usually significant only among the most extreme cytotypes of each subspecies, but, even in this case, the high overlapping ranges prevent their distinction.

https://www.mdpi.com/2073-4425/12/6/906/pdf

Genome Size, Chromosome Number and Morphological Data Reveal Unexpected Infraspecific Variability in Festuca (Poaceae).

One of the most important microorganisms in the soil are the mycorrhizal fungi; however, little research exists regarding mycorrhizal symbiosis on the South American Mediterranean-type ecosystem (MTE) – also commonly known as Chilean matorral. The aims of this chapter are to highlight and compile the existing and arising knowledge on mycorrhizal symbiosis of the Chilean MTE, as well as detect knowledge gaps and propose future directions of research. So far, the mycorrhizal type of some plant species of the Chilean matorral is known. Regarding arbuscular mycorrhizal symbiosis, there are few investigations on mycorrhizal ecology and applied research with agricultural purposes and more is in development. Some ectomycorrhizal and orchid mycorrhizal symbiosis research is available on ecological concerns about biodiversity patterns with applied potential for conservation. The lack of studies on ericoid mycorrhiza was detected. Finally, in spite of the ecological diversity studies carried on the mycorrhiza from the Chilean MTE, further studies quantifying the mycorrhizal contribution should be performed so as to be applied on conservation and sustainable systems.

Mycorrhizas in the South American Mediterranean-Type Ecosystem: Chilean Matorral

Cytogenetic diversity in the polyploid complex Linum suffruticosum s.l. (Linaceae)

We acknowledge the Severo Ochoa Program for Spanish Centers of Excellence in R+D+I (SEV‐2012‐0262) and the Vice‐Rectorate for Research of the University of Seville through operating grants for the conference.

Present and future of ecological and evolutionary research in mediterranean-type ecosystems: Conclusions from the last international mediterranean ecosystems conference

Erika Olmedo-Vicente

Papers

Cytogenetic diversity in the polyploid complex Linum suffruticosum s.l. (Linaceae)

Present and future of ecological and evolutionary research in mediterranean-type ecosystems: Conclusions from the last international mediterranean ecosystems conference