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Results for “mutualism breakdown”

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PubMed2026

Concurrent ecological and evolutionary processes contribute to mutualism breakdown between legumes and rhizobia.

Though they jointly shape community responses to environmental perturbations, ecology and evolution are often examined separately, even in microorganisms where both occur over short timescales. Here we examine ecological and evolutionary responses to 33 years of nitrogen fertilization using the legume-rhizobium mutualism. Pairing a manipulative inoculation study with full-length 16S rRNA gene amplicon sequencing and structural equation modeling allows us to synthesize across biological scales: whole bacterial community, genus Rhizobium, Rhizobium ASVs, and symbiosis plasmids. Clover's preferred partner decreases in N-addition soils, limiting host growth, while a diverse and largely uncharacterized Rhizobium community increases. This ecological change is compounded by a concurrent evolutionary degradation of symbiont partner quality via changing frequencies of symbiotic plasmids. Ecological (rarer symbionts) and evolutionary (inferior symbionts) processes each accounted for roughly half of this loss of host benefit, revealing that ecology and evolution jointly shape mutualism breakdown over the short timescales typical of microbial systems.

ecology↗

PubMed2016

Genomic heterozygosity and hybrid breakdown in cotton (Gossypium): different traits, different effects.

BACKGROUND: Hybrid breakdown has been well documented in various species. Relationships between genomic heterozygosity and traits-fitness have been extensively explored especially in the natural populations. But correlations between genomic heterozygosity and vegetative and reproductive traits in cotton interspecific populations have not been studied. In the current study, two reciprocal F2 populations were developed using Gossypium hirsutum cv. Emian 22 and G. barbadense acc. 3-79 as parents to study hybrid breakdown in cotton. A total of 125 simple sequence repeat (SSR) markers were used to genotype the two F2 interspecific populations. RESULTS: To guarantee mutual independence among the genotyped markers, the 125 SSR markers were checked by the linkage disequilibrium analysis. To our knowledge, this is a novel approach to evaluate the individual genomic heterozygosity. After marker checking, 83 common loci were used to assess the extent of genomic heterozygosity. Hybrid breakdown was found extensively in the two interspecific F2 populations particularly on the reproductive traits because of the infertility and the bare seeds. And then, the relationships between the genomic heterozygosity and the vegetative reproductive traits were investigated. The only relationships between hybrid breakdown and heterozygosity were observed in the (Emian22 × 3-79) F2 population for seed index (SI) and boll number per plant (BN). The maternal cytoplasmic environment may have a significant effect on genomic heterozygosity and on correlations between heterozygosity and reproductive traits. CONCLUSIONS: A novel approach was used to evaluate genomic heterozygosity in cotton; and hybrid breakdown was observed in reproductive traits in cotton. These findings may offer new insight into hybrid breakdown in allotetraploid cotton interspecific hybrids, and may be useful for the development of interspecific hybrids for cotton genetic improvement.

Chromosomes, Plant↗

PubMed1979

The consciously rejected child: legal and social issues.

With increasing frequency, we are observing the phenomenon of the parentally abandoned or rejected child. This can in large measure be attributed to several social/historical developments in American society (Crandall and Grossberg, 1978). Important factors contributing to the phenomenon include the much publicized "breakdown" of traditional family structures; increasing divorce rates; the urbanization of the American population, which creates a cloak of social anonymity; and the establishment of a state/federal welfare bureaucracy, which in part supplants the caretaking functions traditionally carried out by parents. Children who become the victims of parental abandonment find themselves in circumstances in which they come to the attention of an remain, at least for a time, the responsiblity of the legal system and the mental health professions. The interaction of these two institutions, with their overlapping obligations of responsibility toward protecting children, often creates its own problems. Problems arise in part from the somewhat different "interests" of children whom the legal and mental health professions seek to protect and in part from a lack of mutual understanding and knowledge concerning the respective goals, duties, and professional obligations of the two professions. By becoming familiar with the complexity of legal issues which surround the topic of intrafamily relationships in general and parental rights in particular, the psychiatric practitioner can anticipate certain problems which might occur during the course of treatment and can in some instances specify conditions or introduce safeguards in order to minimize the impact of legal intrusions upon the treatment program. The following discussion is designed to help the practitioner to achieve these goals.

Child↗