Journal of Evolutionary Biology最新文献

Modularity and developmental (in)stability have the potential to influence phenotype production and, consequently, the evolutionary trajectories of species. Depending on the environmental factors involved and the buffering capacity of an organism, different developmental outcomes are expected. Cactophilic Drosophila species provide an established eco-evolutionary model with well-studied ecological conditions, making them ideal for studying these phenomena. Here, we investigated how variations in larval diet and exposure to alkaloids on primary and secondary host plants affect the degree of integration/modularity and fluctuating asymmetry (a proxy for developmental instability) of wing shape in two sibling species with different degrees of specialization: D. buzzatii (generalist) and D. koepferae (specialist). Additionally, we compared the anterior-posterior modular configuration with a recently proposed proximal-distal modular configuration. Our results revealed greater independence among proximal-distal modules compared to anterior-posterior modules. Moreover, we observed sex-specific responses, with males exhibiting greater susceptibility to stressful environments than females. Each species showed a particular trait pattern across treatments: D. buzzatii showed increased integration and fluctuating asymmetry when reared in a nutrient-poor, alkaloid-rich secondary host, while D. koepferae displayed similar responses in novel environments characterized by double doses of alkaloids on the secondary host plant. These findings align with the generalist-specialist paradigm, suggesting that specialists may be challenged by novel environments, whereas generalists may be more affected by stressful conditions. Our study highlights the importance of considering each part of the proximal-distal wing axis independently, and the need to consider ecological-evolutionary history when investigating the relationship between complex phenotypic traits and environmental stress.

In ovipositing animals, egg placement decisions can be key determinants of offspring survival. One oviposition strategy reported across taxa is laying eggs in clusters. In some species, mothers provision eggs with diffusible defence compounds, such as antimicrobials, raising the possibility of public good benefits arising from egg clustering. Here we report that Drosophila melanogaster females frequently lay eggs in mixed maternity clusters. We tested two hypotheses for potential drivers of this oviposition behaviour: (i) the microbial environment affects fecundity and egg placement in groups of females; (ii) eggs exhibit antimicrobial activity. The results partially supported the first hypothesis. Females reduced egg laying, but did not alter egg clustering, on non-sterile substrates that had been naturally colonised with microbes from the environment. However, oviposition remained unaffected when the substrate community consisted of commensal (fly-associated) microbes. The second hypothesis was not supported. There was no evidence of antimicrobial activity, either in whole eggs or in soluble egg surface material. In conclusion, while we found no behavioural or physiological evidence that egg clustering decisions are shaped by the opportunity to share antimicrobials, females are sensitive to their microbial environment and can adjust egg laying rates accordingly.

Differences in habitat use impose ecological constraints which in turn lead to functional and morphological differences through adaptation. In fact, a convergent evolutionary pattern is evident when species exhibit similar responses to similar environments. In this study we examine how habitat use influences the evolution of body shape in lizards from the family Lacertidae. We divided our species set into two categories: ground-dwellers and climbers, which encompasses the verticality and horizontality aspects of the habitat. We performed phylogenetic comparative analyses employing 186 species and seven linear morphological traits. Our results show contrasting patterns between head and limb shape, which are considered distinct functional blocks. We observed differences in forelimb proportions, but not in hindlimb length, contrary to what was documented in other lizard groups, demonstrating a novel axis in the limb-locomotion-habitat relationship in this family. In addition, a clear effect of habitat use on head shape was detected. We observed that climbing species present on average flatter heads than ground-dwelling species, as well as different evolutionary trajectories. These findings suggest the complex interplay between habitat use and morphological evolution in lizards, highlighting how distinct selective pressures drive divergent adaptations in different functional traits.

Walnut is a significant woody oil tree species that has been increasingly affected by anthracnose in recent years. Effective anthracnose control is crucial for walnut yield and quality, which requires a comprehensive understanding of the response mechanisms to Colletotrichum gloeosporioides. The PR10/Bet v1-like proteins are involved in defense against various disease, therefore, in this study, 7 JrBet v1s were identified from the walnut transcriptome (named JrBet v1-1~1-7), whose open reading frame (ORF) was 414~483 bp in length with isoelectric point ranging from 4.96 to 6.11. These JrBet v1s were classified into three groups, with the MLP/RRP and Dicot PR-10 subfamilies each comprising three members (the largest ones), indicating that the proteins within these two subfamilies may have evolved from a shared ancestral gene within the broader PR10/Bet v1 protein family. The cis-elements in the promoters of JrBet v1s were involved in response to hormones, coercive, and plant growth metabolism. Most JrBet v1s could be significantly upregulated by walnut anthracnose, JrBet v1-1, JrBet v1-2, JrBet v1-4, and JrBet v1-6 peaked at 12 days of anthracnose stress, showing a 2.85- to 63.12-fold increase compared to the control, while JrBet v1-3, JrBet v1-5 and JrBet v1-7 peaked at 9 days, with a 3.23- to 27.67-fold increase. Furthermore, the significant corelation of the upregulation under anthracnose stress of JrBet v1s and JrChit02-1 as well as JrChit02-2, the genes encoding chitinase, suggesting that during the long process of microevolution in walnut-C. gloeosporioides interactions, walnut has developed a Bet v1-chitinase defense mechanism to counteract pathogen invasion.

Polymorphic short insertions and deletions (INDELs ≤ 50 bp) are abundant, although less common than single nucleotide polymorphisms (SNPs). Evidence from model organisms shows INDELs to be more strongly influenced by purifying selection than SNPs. Partly for this reason, INDELs are rarely used as markers for demographic processes or to detect divergent selection. Here, we compared INDELs and SNPs in the intertidal snail Littorina saxatilis, focusing on hybrid zones between ecotypes, in order to test the utility of INDELs in the detection of divergent selection. We computed INDEL and SNP site frequency spectra (SFS) using capture sequencing data. We assessed the impact of divergent selection by analysing allele frequency clines across habitat boundaries. We also examined the influence of GC-biased gene conversion because it may be confounded with signatures of selection. We show evidence that short INDELs are affected more by purifying selection than SNPs, but part of the observed SFS difference can be attributed to GC-biased gene conversion. We did not find a difference in the impact of divergent selection between short INDELs and SNPs. Short INDELs and SNPs were similarly distributed across the genome and so are likely to respond to indirect selection in the same way. A few regions likely affected by divergent selection were revealed by INDELs and not by SNPs. Short INDELs can be useful (additional) genetic markers helping to identify genomic regions important for adaptation and population divergence.

The force of selection describes the sensitivity of population growth to changes in life history parameters, with a focus usually on the survival probabilities from one age class to the next. Importantly, according to Hamilton the force of selection generally decreases after the onset of reproduction, thereby providing a possible explanation for patterns of senescence. A second characteristic feature is that the force of selection remains constant up to the age of first reproduction. This latter observation, however, rests on the assumption that offspring become independent from their parents right after birth. I show here in a minimal model that if offspring are fully reliant on their parents, either during early embryonal development or via parental care at later stages, and during this time prevent their parents from entering a new bout of reproduction, the force of selection on offspring survival generally increases up until the age at which offspring become independent. This provides a possible explanation for the commonly observed pattern of decreasing mortality during early ontogeny. Furthermore, genes acting during recurrent life stages are observed to experience a heightened force of selection compared with genes that act strictly age specifically, demonstrating the need to develop a mechanistic understanding of gene activation patterns through which to consider life history evolution.

Dispersal is a key demographic parameter that plays an important role in determining spatial population dynamics and genetic structure. Linking differences in dispersal patterns to life-history traits is often confounded by inconsistent environmental pressures experienced by different populations. To explore the relationship between dispersal and life history, we focus on a site where oviparous and viviparous lineages of the common lizard (Zootoca vivipara) are found adjacent to each other. We take advantage of this shared environment to investigate parity-specific dispersal patterns using high-resolution, individual-level spatial-genetic autocorrelation and population genomic approaches (11,726 single nucleotide polymorphisms; 293 oviparous and 310 viviparous individuals). We found isolation-by-distance patterns to be present in both the oviparous and viviparous populations. Density was 2.5 times higher in the oviparous population than the viviparous one, though heterozygosity and genetic diversity measures were similar in the two populations. We found marked differences in the extent of genetic neighbourhoods between the lineages, with the viviparous population showing both dispersal (σ) and spatial-genetic autocorrelation (Moran's I) at 2-fold greater geographic distances than the oviparous population. We found clear evidence of male-biased dispersal from genetic estimates in the viviparous population. In the oviparous population, evidence of male-biased dispersal was weak or absent. These differences are likely to be closely linked to specific requirements of the alternative reproductive strategies and may be the demographic consequences of mother-offspring interactions. Fine-scale geographic and individual-level measures are essential to understanding parity mode differences at microevolutionary scales and to better identifying their ecological and evolutionary impacts.

Theoretical work suggests that reinforcement can cause the strengthening of prezygotic isolation in sympatry by mitigating the costs of maladaptive hybridization. However, only a handful of studies have simultaneously tested multiple predictions of this theory in natural populations. We investigated reinforcement in a mottled hybrid zone between the damselflies Ischnura elegans and Ischnura graellsii, which are characterized by incomplete and asymmetric reproductive isolation and exhibit reproductive character displacement in mating-related structures. We tested the conditions for reinforcement by quantifying whether hybridization was costly and prezygotic isolation stronger in sympatry compared with allopatry. Additionally, we investigated two specific predictions of reinforcement: (a) greater premating asymmetries in sympatry; and (b) weaker postzygotic isolation in sympatry than in allopatry. Our findings indicate the presence of maladaptive hybrids, which suggests Bateson-Dobzhansky-Müller incompatibilities in allopatry. We also found that reinforcement has strengthened mechanical isolation, at least in one direction in sympatry. We observed evidence for greater premating asymmetries in sympatry than in allopatry, which is consistent with reinforcement. However, fully testing the prediction of weaker postzygotic isolation in sympatry compared to allopatry was hindered by the highly asymmetrical levels of reproductive isolation between the two reciprocal cross directions. Our study highlights a case where reinforcement and heterospecific gene flow exert opposite effects on reproductive isolation between reciprocal crosses, where reinforcement increases reproductive isolation in one direction while gene flow weakens it in the opposite direction.