Biology subjects

Alvarez, H. A.

Publications and source records attributed to Alvarez, H. A..

9 recordsLinked to original sources

bioRxiv2025

Effects of elevation and microclimatic temperatures on butterfly-flower interaction networks in a Mediterranean mountain range

O_LIResearching the properties of mutualistic networks over environmental gradients is a promising but underexplored means to test how global change can affect ecosystem assembly and functioning. We examined how elevation and microclimate influenced butterfly-flower interaction networks at the hottest time of year in a Mediterranean mountain range. C_LIO_LIThroughout July 2023, we recorded weekly butterfly-flower interaction networks from 36 transects in nine sites, across an 800 m elevation gradient in the Sierra de Guadarrama (Central Spain). We quantified the connectance, nestedness, modularity and robustness to species loss of networks, and related these descriptors using Generalized Additive Mixed Models to elevation, microclimate temperature (modelled using Microclima), date and time of day. C_LIO_LIThe networks were dominated at all sites by one or two abundant butterfly and flower species, but these varied with elevation. Butterfly networks were more robust to plant species loss at higher elevations, where communities showed increased linkage density. Butterfly-plant networks became less nested at higher microclimatic temperatures in July. Network properties also varied through the day, with connectance decreasing markedly from morning to afternoon. C_LIO_LIIn the Mediterranean mountains studied, summer butterfly-flower interaction networks were more resilient to disturbance at high elevations and in cooler microclimates. Nectar availability could become an important limiting factor for insects in a warming climate, and understanding the mechanisms influencing the properties of flower visitor networks is therefore likely to become increasingly important for adapting the conservation of insects to climate change. C_LI

ecology↗

bioRxiv2022

Do Neotropical adult dobsonflies (Megaloptera, Corydalidae) feed on solid material in the nature? Information from a gut content study

Females of two species of corydalids (Megaloptera), Corydalus magnus Contreras-Ramos, 1998 and Platyneuromus soror (Hagen, 1861), are studied with the aim to determine if solid food is present in their guts, which would indicate the existence of feeding on solid food during the imaginal life in nature. Gut anatomical architecture is also studied and described for females of both species, showing no peculiarities regarding the existing information in other close related species and confirming that digestive morphology is conserved in Megaloptera, as previously reported in literature. No significant solid food was detected in any of the species, so in the nature, they may rely more on liquid sources and/or fat reserves produced in the larval stage for the energetic requirements of adult life.

ecology↗

bioRxiv2022

Effects of diversifying the planting period of maize on herbivorous and their natural enemies

Knowledge of the specific insect densities during crop development is necessary to perform appropriate measures for the control of insect pests and to minimize yield losses. In a previous study, both spatial and temporal approaches were adopted to analyse the influence of landscape structure and field variables on herbivore and predatory insects on maize. Both types of variables influenced insect abundance, but the highest effect was found with maize phenology. Given that the field planting date could modulate the influence produced by the structure of the landscape on herbivores and predatory insects, analyses of population dynamics must be performed at both the local and landscape levels. The anterior prompted us to study these aspects in the two common planting periods (early and late) in northern Spain. The present study tests the hypothesis that the period of maize planting could have a higher effect than phenology or interannual variation on the abundance of natural enemies and herbivores on maize. Our results showed that only the abundances of other herbivore thrips and Syrphidae were significantly different between the two planting periods. Moreover, we found significant effects of planting period when we performed yearly analysis in 2015 for Coccinellidae and Chrysopidae and in 2016 and 2017 for Aeolothrips sp. Most of the taxa had abundance peaks in earlier growth stages, which are related to pollination (before or during), while only Stethorus punctillum and Syrphidae increased later in the season. Furthermore, Frankliniella occidentalis, aphids, Syrphidae and Coccinellidae registered higher abundances in fields sown in the late planting period than in the rest of the insect species. The results of the present study highlight the effects of sowing dates on insect dynamics in maize. HighlightsO_LIHerbivorous and natural enemy abundance peaks in earlier growth stages. C_LIO_LIAbundance of thrip and Syrphidae were different between the two planting periods. C_LIO_LIAbundance of Coccinellidae, Chrysopidae and Aeolothrips sp. was different when performed yearly analysis. C_LI

ecology↗

bioRxiv2022

Potential geographic distribution and ecological niche of the insect order Megaloptera: the case of the neartic-neotropical transition zone

The dobsonflies (Megaloptera, Corydalidae) are an interesting group of insects, but among the New World dobsonflies, it is not known the effect of the Neartic-Neotropical transition zone on their biogeographic distribution. Here we studied at the species level, the records on the geographic range of the dobsonflies that occurred in and near the transition zone. We presented potential geographic distributions based on ecological niche models for several species of dobsonflies. Results suggested that the geographic range of dobsonflies in the transition zone is associated to mountainous formations and that most species favor warm climates with higher precipitation rates. Climate types tend to be important for species that show narrow geographic ranges, but precipitation tends to be the most important variable to explain species dispersion. Overall, our models support the dispersion of dobsonflies from the Neotropics to North America and explain the two endemic species in Mexico as the result of the formation of the transition zone.

ecology↗

bioRxiv2021

Plant morphometry matches beetle diversity: effects of natural adjacent vegetation on grain Amaranth crop under small-holder conditions

Grain Amaranth, Amaranthus hypochondriacus L., is an emerging arable crop cultivated worldwide. One way to obtain resources from the crop, other than grain, is to grow Amaranths in the dry season and harvest only the leaves. In this environmental condition the response of an Amaranth agroecosystem to the presence of natural and semi-natural habitats or other crops has not been studied yet. We analysed the response of (1) Amaranth morphometry and (2) alpha and beta diversity of beetles to the nearness of adjacent vegetation and natural habitats (such as deciduous forest) at the small-holder conditions. Our results showed that A. hypochondriacus crop plants responded positively to the presence of an ecotone (adjacent vegetation) and the natural habitat (deciduous forest), i.e., A. hypochondriacus plants grew bigger in the section nearest to adjacent vegetation, which was a pattern consistent in time. Moreover, for beetles (considered as a bioindicator group), richness was different amongst the study areas and negatively followed the gradient of perturbation. These results suggest that Amaranth crop is sensitive to the presence of natural and semi-natural habitats but not to other crops in the dry season. In addition, beetles match the response of Amaranth plants. This is the first time that this type of data is recorded in grain Amaranth agroecosystem and it will help to understand the interaction amongst grain Amaranth agroecosystems, biodiversity, and natural adjacent vegetation to boost ecosystem services.

ecology↗

bioRxiv2021

Ground cover presence in organic olive orchards affects the interaction of natural enemies against Prays oleae, promoting an effective egg predation

The olive moth, Prays oleae, is one of the most common insects that damages olives in the Mediterranean region. The establishment of ground cover within olive orchards has been promoted in this region in recent years to avoid erosion and soil degradation. Nevertheless, its role as a shelter for natural enemies of pests has been controversial. In this study, we have investigated the effectiveness of the biological control of P. oleae in organic olive orchards with ground cover (mowed) and without ground cover (tilled). For this, (1) we assessed the relationship between predated eggs and the abundance of natural enemies in both types of orchards; (2) we compared both the potential damage of the pest and the egg hatching in the two types of orchards; and (3) we examined the interaction amongst families of natural enemies and P. oleae (as adults and as predated eggs). The results showed that there is a high rate of predation in the studied olive orchards, 81% of the eggs were predated, 12.2% hatched, and 6.9% were live eggs. However, mowed orchards were more effective for controlling P. oleae by means of egg predation rather than tilled orchards, i.e., in mowed orchards, whilst the potential damage of the pest was higher, egg hatching was rather low. The structure of the adult arthropod community, i.e., the composition and abundance of families of natural enemies did not differ between the orchards, but the abundance of the families Anthocoridae, Miridae and Scelionidae was significantly higher in the mowed orchards. Finally, the interaction amongst natural enemies and P. oleae showed that the families that better explained the effects on egg predation were Aeolothripidae, Anthocoridae, Miridae, Chrysopidae (predators), and Formicidae (omnivore). We discuss the results in terms of ecological interactions of trophic guilds and we conclude that the establishment and maintenance of ground cover in organic olive orchards, at least in June and July, is of great significance because it positively affects the egg predation of P. oleae. This effect is especially significant when there is a low abundance of natural enemies in the olive orchards.

ecology↗

bioRxiv2021

Habitat complexity in organic olive orchards modulates the abundance of natural enemies but not the attraction to plant species

Semi-natural habitat complexity and organic management could affect the abundance and diversity of natural enemies and pollinators in olive orchards. Nonetheless, in such agroecosystems the effect of plant structure, plant richness, and plant attraction on the arthropod fauna has been poorly documented. Here we evaluate the influence of those effects jointly as an expression of arthropod abundance and richness in olive trees, ground cover, and adjacent vegetation within organic olive orchards. For this, we used generalized linear models and non-metric multidimensional scaling (NMDS) integrating generalized additive models. Our results suggest that natural enemies and pollinators are mainly attracted to A. radiatus, D. catholica, and L. longirrostris within ground cover and G. cinerea speciosa, Q. rotundifolia, R. officinalis, T. zygis gracilis, and U. parviflorus within adjacent vegetation. Accordingly, habitat complexity showed a positive relationship with the abundance of key families of natural enemies and pollinators but not with the number of taxa. NMDS showed that plant richness and plant arrangement and scattering affected the key families differently, suggesting that each key family responds to their individual needs for plant resources but forming groups modulated by complexity. This pattern was especially seeing in predators and omnivores. Our findings support that the higher the plant richness and structure of a semi natural-habitat within an olive orchard, the higher the abundance and richness of a given arthropod community (a pattern found in natural ecosystems). The information presented here can be used by producers and technicians to increase the presence and abundance of natural enemies and pollinators within organic olive orchards, and thus improve the ecosystem services provided by semi-natural habitats. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=55 SRC="FIGDIR/small/429588v1_ufig1.gif" ALT="Figure 1"> View larger version (10K): org.highwire.dtl.DTLVardef@1937910org.highwire.dtl.DTLVardef@f1365borg.highwire.dtl.DTLVardef@279a14org.highwire.dtl.DTLVardef@1f4a476_HPS_FORMAT_FIGEXP M_FIG C_FIG

ecology↗

bioRxiv2019

A dynamic cell recruitment process drives growth of the Drosophila wing by overscaling the Vestigial expression pattern

Organs mainly attain their size by cell growth and proliferation, but sometimes also grow through recruitment of undifferentiated cells. Here we investigate the participation of cell recruitment in establishing the pattern of Vestigial (Vg), the product of the wing selector gene in Drosophila. We find that the Vg pattern overscales along the dorsal-ventral (DV) axis of the wing imaginal disc, i.e., it expands faster than the DV length of the pouch. The overscaling of the Vg pattern cannot be explained by differential proliferation, apoptosis, or oriented-cell divisions, but can be recapitulated by a mathematical model that explicitly considers cell recruitment. By impairing cell recruitment genetically, we find that the Vg pattern almost perfectly scales and adult wings are approximately 20% smaller. Furthermore, using fluorescent reporter tools, we provide direct evidence that cell recruitment takes place in a specific time between early and mid third-instar larval development. Altogether, our work quantitatively shows when, how, and by how much cell recruitment shapes the Vg pattern and drives growth of the Drosophila wing.

developmental biology↗

bioRxiv2018

Single Cell Transcriptomics of Pancreatic Cancer Precursors Demonstrates Epithelial and Microenvironmental Heterogeneity as an Early Event in Neoplastic Progression

BackgroundEarly detection of pancreatic ductal adenocarcinoma (PDAC) remains elusive. Precursor lesions of PDAC, specifically, intraductal papillary mucinous neoplasms (IPMNs) represent a bona fide pathway to invasive neoplasia, although the molecular correlates of progression remain to be fully elucidated. Single cell transcriptomics provides a unique avenue for dissecting both the epithelial and microenvironmental heterogeneity that accompany multistep progression from non-invasive IPMNs to PDAC.\n\nMethodsSingle cell RNA-sequencing was performed through droplet-based sequencing on 5,403 cells from two low-grade IPMNs (LGD-IPMN), two high-grade IPMNs (HGD-IPMN), and two PDACs (all surgically resected).\n\nResultsAnalysis of single cell transcriptomes revealed heterogeneous alterations within the epithelium and the tumor microenvironment during the progression of non-invasive dysplasia to invasive cancer. While HGD-IPMNs expressed many core-signaling pathways described in PDAC, LGD-IPMNs harbored subsets of single cells with a transcriptomic profile that overlapped with invasive cancer. Notably, a pro-inflammatory immune component was readily seen in low-grade IPMNs, comprised of cytotoxic T-cells, activated T-helper cells, and dendritic cells, which was progressively depleted during neoplastic progression, accompanied by infiltration of myeloid-derived suppressor cells. Finally, stromal myofibroblast populations were heterogeneous, and acquired a previously described tumor-promoting and immune-evading phenotype during invasive carcinogenesis.\n\nConclusionsThis study demonstrates the ability to perform high resolution profiling of the transcriptomic changes that occur during multistep progression of cystic PDAC precursors to cancer. Notably, single cell analysis provides an unparalleled insight into both the epithelial and microenvironmental heterogeneity that accompany early cancer pathogenesis, and might be a useful substrate to identify targets for cancer interception.

pathology↗