A set D of vertices in a connected graph G is a semitotal dominating set if D is a dominating set of G and every vertex in D is within distance two of some vertex in D. If, in addition, D is an independent set, then D is called an independent semitotal dominating set of G. The (independent) semitotal domination number of G, denoted by γt2(G) (respectively, it2(G)), is the minimum cardinality among all (independent) semitotal dominating sets of G. By definition, we have that γt2(G)≤it2(G) for every connected non-complete graph G. In this article, we establish lower and upper bounds for it2(T) when T is a tree of order at least three, and we obtain an improved lower bound for it2(T) when T is a binary tree. Finally, we provide a constructive characterization of all trees T for which it2(T)=γt2(T).
The effects of habitat fragmentation on biodiversity are widely debated. Some studies report positive effects, whereas others link habitat fragmentation to biodiversity loss. “Fragmentation per se” refers to habitat fragmentation independently of habitat loss, or when its effect is controlled, and mainly relates to how habitat patches are spatially distributed (i.e. habitat configuration) and how this organization influences biodiversity. Here we evaluated the habitat amount hypothesis, which postulates that habitat cover is the main factor determining species diversity in fragmented landscapes. We analyzed the effects of landscape structure of a tropical dry forest in the Colombian Caribbean region on the taxonomic and (SES) functional richness of medium- to large-bodied mammals. We assessed 256 landscapes along a gradient of forest cover. We calculated landscape composition (forest cover) and configuration metrics (number of patches and edge density) in multiple nested scales. For each landscape, we estimated species richness, forest-dependent species richness, non-forest-dependent species richness, and the standardized effect size of functional richness. We evaluated the effects of landscape structure using AICc-based model comparison and model averaging. We found that species richness was positively affected by edge density, negatively affected by the number of patches, and moderately positively affected by forest cover. We also found that forest-dependent species richness was positively related to forest cover, whereas non-forest-dependent species richness showed a positive effect of edge density. We also detected a moderate negative effect of the number of patches on the standardized effect size of functional richness. These results indicate that the habitat amount hypothesis is not fully supported and suggest that conservation strategies should prioritize preserving and increasing the total amount of habitat, while also considering landscape configuration in tropical dry forest of the Colombian Caribbean.
Despite swine dysentery’s relevance in the pork industry, there are still gaps in our understanding of its pathogenesis and the impact of the infection in the gut. This study aimed to characterize the in vivo colonic metabolome of pigs experimentally infected with Brachyspira hyodysenteriae at the onset of fecal shedding (Early_inf group, n = 6) and during acute clinical disease characterized by mucohemorrhagic diarrhea (Acute_inf group, n = 8) compared with non-infected controls (n = 16). The metabolic profile of the colonic contents changed progressively with disease severity, showing an intermediate pattern in the Early_inf group between the control and the Acute_inf groups (p < 0.05). In acute disease, the metabolome was defined by increased concentrations of amino acids, carnitine derivatives, arachidic acid, 1,2-butanediol, and lactic acid, along with decreased levels of anti-inflammatory compounds. In the Early_inf group, increases were observed in amino acids, organic acids, amines, myo-inositol, quinoline, and 1,2-butanediol, whereas linolenic acid and oxalic acid decreased. Integrated analysis of the colonic metabolome and metagenome revealed a strong correlation between metabolic and microbial profiles, particularly in the Acute_inf group, where differential metabolites were associated with B. hyodysenteriae, Campylobacter hyointestinalis, and Velocimicrobium ethanolgignens. Metabolites showed high predictive potential for the disease stage, with lactic acid and arachidic acid being key markers of acute infection and dihydroxyacetone and leucine distinguishing early infection. Overall, this study reveals significant alterations in the colonic metabolome and its association with the microbiota during swine dysentery, providing new insights into the pathophysiology of the disease and contributing to the development of improved prevention and treatment strategies.
Understanding how resource users perceive and negotiate sustainability is essential for designing legitimate conservation governance. This study explores recreational hunters' preferences for sustainability certification in Spain using a discrete choice experiment. Data were collected from 621 hunters representing both big game and small game modalities. Results show that hunters consistently prioritise ecological criteria-such as game population conservation, habitat management, and wild genetics-yet support for certification is conditional on maintaining satisfactory hunting outcomes. Pro-sustainability attitudes coexist with achievement-oriented motivations, with conservation valued when it sustains continuity, fairness, and authenticity of the hunting experience. These findings highlight how ecological and experiential rationalities can align rather than conflict. By revealing the conditions under which certification is perceived as acceptable, the study shows how sustainability standards can function as information-based governance tools that enhance legitimacy, trust, and adaptive management in recreational hunting systems.
