Natural Dispersal Research Articles

Considerations about the Geographic Distribution of Histoplasma Species.

Histoplasmosis is a mycotic infection principally affecting pulmonary tissue; sometimes, histoplasmosis can progress into a systemic disease. This infection involves immunocompetent and immunosuppressed human and other mammalian hosts, depending on particular circumstances. Histoplasmosis infection has been documented worldwide. The infection is acquired by inhaling infective mycelial propagules of the dimorphic fungus Histoplasma capsulatum. New reports of clinical cases of histoplasmosis in extreme latitudes could be related to human social adaptations and climate changes in the world, which are creating new favorable environments for this fungus and for bats, its major natural reservoirs and dispersers. Histoplasma has been isolated from most continents, and it is considered a complex of cryptic species, consisting of various groups of isolates that differ genetically and correlate with a particular geographic distribution. Based on updated studies, Histoplasma taxonomy is adjusting to new genetic data. Here, we have suggested that Histoplasma has at least 14 phylogenetic species distributed worldwide and new genotypes that could be under deliberation. Histoplasma's geographic radiation began in South America millions of years ago when the continents were joined and the climate was favorable. For fungal spreading, the role of bats and some birds is crucial, although other natural factors could also participate.

Analysis of the Orchidaceae Diversity in the Pululahua Reserve, Ecuador: Opportunities and Constraints as Regards the Biodiversity Conservation of the Cloud Mountain Forest.

The Pululahua Geobotanical Reserve is a protected natural area in the cloud mountain forest of Ecuador, so rich in orchid species despite being a volcanic area still under threat of volcanic activity. A comparative biodiversity study of orchids was carried out in two different sectors, Chaupisacha (CH) and La Reventazón (LR). Data were collected in 1 ha plots in each sector, in which all the orchids found were counted and two individuals of each species were retained. Immature individuals were conserved in a plant nursery until flowering. In CH, there were 922 individuals grouped into 24 genera and 55 species, while LR had 9196 individuals grouped into 26 genera and 46 species; only 14 species were found in both sectors. Different density and diversity indexes were calculated. The density (ind./100 m2) of CH was 0.96, while that of LR was 185.92. Simpson’s diversity (1 − λ) attained CH 0.903 ± 0.01 and LR 0.85 ± 0.01. The orchid diversity measured by the Shannon-Wiener diversity index (H′) was 1.29 for CH, differing significantly from that of LR (H′ 1.02). The medium equity (Jaccard’s J′) found was 0.61 in CH and 90.78 in LR. Limitations as regards the natural dispersion of orchids seemed to favor endemism. Some species, such as Dracula felix and Restrepia guttulate, are threatened with disappearance from the wild or are vulnerable, as is the case for Epidendrum polyanthogastrium. A lack of information on the phenology and anthropic impacts in the area limit the conservation of species, signifying that new protected figures and seed banks are necessary, especially in CH, owing to its high diversity of orchids.

Wind dispersal of seeds of Parthenium hysterophorus L. (Asteraceae) contributes to its steady invasion and spread

AbstractWind dispersal is considered to be a potentially important mode of spread for parthenium weed (Parthenium hysterophorus L.), an invasive Asteraceae herb of worldwide significance. However, empirical evidence of the role of wind dispersal on the seeds (achenes) of parthenium weed in natural landscapes is lacking. The results of a simulation study undertaken at a wind tunnel facility, Australia, indicated that the dispersal distance of parthenium weed achenes is largely determined by wind velocity (109–131% increase in distance where wind velocity is doubled) and plant release height (75–80% increase when release height is doubled). Glasshouse harvested achenes released from 1 m in height could travel up to 2 m under a 2 m s−1 wind velocity, with the majority of achenes reaching more than 1 m. Smaller‐sized achenes travelled 5% further than larger‐sized achenes. The terminal velocity was calculated to be 1.256 ± 0.006 m s−1, indicating a moderate wind dispersal ability for the weed. A complementary field study in Southeast Queensland, Australia, indicated that the cumulative wind velocity and wind direction, instead of the mean wind velocity, determined the direction of dispersal of the achenes. Further post‐dispersal surveys suggested the number of achenes outside of a standing population declined rapidly as distance from the population increased. Most achenes were dispersed less than 2 m from their parent plant, while the maximum distance achieved was less than 5 m under natural conditions in North Queensland. In conclusion, the natural wind dispersal of parthenium weed consists of small, but measurable increments each year, thus contributing to the weed proliferation and spread at the landscape scale level.

Nonrelativistic effective field theories with enhanced symmetries and soft behavior

We systematically explore the landscape of nonrelativistic effective field theories with a local S-matrix and enhanced symmetries and soft behavior. The exploration is carried out using both conventional quantum field theory methods based on symmetry arguments, and recently developed on-shell recursion relations. We show that, in contrary to relativistic theories, enhancement of the soft limit of scattering amplitudes in nonrelativistic theories is generally not a byproduct of symmetry alone, but requires additional low-energy data. Sufficient conditions for enhanced scattering amplitudes can be derived by combining symmetries and dispersion relations of the scattered particles. This has direct consequences for the infrared dynamics that different types of nonrelativistic Nambu-Goldstone bosons can exhibit. We then use a bottom-up soft bootstrap approach to narrow down the landscape of nonrelativistic effective field theories that possess a consistent low-energy S-matrix. We recover two exceptional theories of a complex Schrödinger-type scalar, namely the ℂP1 nonlinear sigma model and the Schrödinger-Dirac-Born-Infeld theory. Moreover, we use soft recursion to prove a no-go theorem ruling out the existence of other exceptional Schrödinger-type theories. We also prove that all exceptional theories of a single real scalar with a linear dispersion relation are necessarily Lorentz-invariant. Soft recursion allows us to obtain some further general bounds on the landscape of nonrelativistic effective theories with enhanced soft limits. Finally, we present a novel theory of a complex scalar with a technically natural quartic dispersion relation. Altogether, our work represents the first step of a program to extend the developments in the study of scattering amplitudes to theories without Lorentz invariance.

Pest categorisation of Toumeyella parvicornis.

The EFSA Panel on Plant Health performed a pest categorisation of Toumeyella parvicornis (Cockerell) (Hemiptera: Coccidae) for the EU territory. This species is not included in EU Commission Implementing Regulation 2019/2072. T. parvicornis is a soft‐scale insect native to North America and has been introduced to the Caribbean region and the EU. It has been present in Italy since 2014 (Abruzzo, Campania, Lazio, and Apulia regions) and in France since 2021 (Provence–Alpes–Côte d'Azur region) and is under official control. It develops on Pinus spp. (Pinaceae), feeding on the needles and twigs, especially on new growth. It is sexually reproductive, has one or more generations each year (three in southern Italy), and adult females overwinter on the Pinus needles. It has a high fecundity, up to 1,014 eggs per female in Italy, with an average of 199 eggs for the summer generation and 730 for the overwintering generation. The main natural dispersal stage is the first instar, which crawls over the plant or may be dispersed further by wind and animals. The species can be transported over longer distances with plants for planting. Large populations cause yellowing, needle loss, reduction in growth and recruitment, flagging, dieback and tree mortality. It has had a significant impact to P. pinea (stone pine) in Italy and caused a catastrophic decline of P. caribbea var. bahamensis (Caribbean pine) in the Turks and Caicos Islands. Adult and immature T. parvicornis could enter the EU with Pinus plants for planting; however, the import of Pinus from third countries where the scale is found is prohibited. Host availability and climate suitability indicate that most of the EU would be suitable for establishment. Phytosanitary measures are available to inhibit further introductions and slow the spread within the EU. T. parvicornis satisfies all the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.

Profile of Myracrodruon urundeuva Volatile Compounds Ease of Extraction and Biodegradability and In Silico Evaluation of Their Interactions with COX-1 and iNOS.

Myracrodruon urundeuva Fr. Allem. (Anacardiaceae) is a tree popularly known as the “aroeira-do-sertão”, native to the caatinga and cerrado biomes, with a natural dispersion ranging from the Northeast, Midwest, to Southeast Brazil. Its wood is highly valued and overexploited, due to its characteristics such as durability and resistance to decaying. The diversity of chemical constituents in aroeira seed has shown biological properties against microorganisms and helminths. As such, this work aimed to identify the profile of volatile compounds present in aroeira seeds. Headspace solid phase microextraction was employed (HS-SPME) using semi-polar polydimethylsiloxane-divinylbenzene fiber (PDMS/DVB) for the extraction of VOCs. 22 volatile organic compounds were identified: nine monoterpenes and eight sesquiterpenes, in addition to six compounds belonging to different chemical classes such as fatty acids, terpenoids, salicylates and others. Those that stood out were p-mentha-1,4, 4(8)-diene, 3-carene (found in all samples), caryophyllene and cis-geranylacetone. A virtual docking analysis suggested that around 65% of the VOCs molar content from the aroeiras seeds present moderate a strong ability to bind to cyclooxygenase I (COX-I) active site, oxide nitric synthase (iNOS) active site (iNOSas) or to iNOS cofactor site (iNOScs), corroborating an anti-inflamatory potential. A pharmacophoric descriptor analysis allowed to infer the more determinant characteristics of these compounds’ conferring affinity to each site. Taken together, our results illustrate the high applicability for the integrated use of SPME, in silico virtual screening and chemoinformatics tools at the profiling of the biotechnological and pharmaceutical potential of natural sources.

Pest categorisation of Pseudococcus cryptus.

The EFSA Panel on Plant Health performed a pest categorisation of Pseudococcus cryptus Hempel (Hemiptera: Pseudococcidae), the citriculus mealybug, for the EU. P. cryptus originates from Southeast Asia but is now established in East Africa, the Middle East and South America. The pest is not currently known to occur in the EU (there was a record once, in 2006, in a zoo/botanical garden from southern Spain). P. cryptus is not listed in Commission Implementing Regulation (EU) 2019/2072. It is polyphagous, feeding on plants in more than 90 genera in 51 families, and exhibits a preference for citrus (Citrus spp.) and palms (especially Cocos nucifera, Elaeis guineensis and Areca catechu). It is an important pest of citrus in Japan and parts of the Middle East, although in Israel, it is controlled by natural enemies. It is sexually reproductive, has six overlapping generations each year in Israel, and each female lays up to approximately 150 eggs, depending on temperature and host species. The main natural dispersal stage is the first instar, which crawls over the host plant or may be dispersed further by wind and animals. Plants for planting, fruits, vegetables and cut flowers provide potential pathways for entry into the EU. Climatic conditions in EU member states around the Mediterranean Sea where there is host plant availability, especially citrus, are conducive for establishment. The introduction of P. cryptus is expected to have an economic impact in the EU through reduction in yield and quality of important crops (mainly citrus) and damage to various ornamental plants. Phytosanitary measures are available to reduce the likelihood of entry and further spread. P. cryptus meets the criteria that are within the remit of EFSA to assess for this species to be regarded as a potential Union quarantine pest.

Mitigation Measures for Invasive Insect Pests on Eucalyptus Spp. in East Africa: A Review

Eucalyptus spp. plantation forestry is expanding rapidly to meet wood and fibre demands internationally, including in Eastern Africa (especially Kenya, Uganda and Tanzania). However, Eucalyptus spp. plantations in eastern Africa are increasingly being damaged by invasive insect pests. In particular, the Australian invasive pests; Gonipterus scutellatus complex (Eucalyptus snout beetle), Leptocybe invasa (Blue gum chalcid), Thaumastocoris peregrinus (Bronze bug), and Glycaspis brimblecombei (Red gum lerp psyllid) pose a serious threat to Eucalyptus spp. plantations in eastern Africa. This is a trend that has also been noted in other parts of Africa and globally. Factors that influence introduction, establishment and spread of Australian invasive insect pests include: the expanding planting of Eucalyptus in intensive plantations over large areas, increased human trade and transport, natural dispersal mechanisms across borders, and a growing pool of established exotic pests in the neighbouring regions. Therefore, there is increasing pressure to develop more effective management strategies for the invasive pests and more rapidly than in the past. Some of the strategies that are employed in pest management and require improvement include: strengthening phytosanitary and quarantine measures at ports of entry, selection and deployment of resistant/tolerant host tree genotypes, and international and regional collaborations to prevent the entry and management of invasive species. In this review we assess on the knowledge generated in recent studies concerning forest pests and further consider methods/policies that could be employed or improved to mitigate the threat of invasive pests associated with Eucalyptus spp. in the Eastern Africa region. Key words: Eucalyptus spp, Pest management, Gonipterus scutellatus, Thaumastocoris peregrinus, Leptocybe invasa, Glycaspis brimblecombei

On possible life-dispersal patterns beyond the Earth

AbstractThe assumption that exoplanets are ‘in equilibrium’ with their surroundings has not given way to life's transmissivity on large spatial scales. The spread of human diseases and the life recovery rate after mass extinctions on our planet, on the other hand, may exhibit spatial and temporal scaling as well as distribution correlations that influence the mappable range of their characteristics. We model hypothetical bio-dispersal within a single Galactic region using the stochastic infection dynamics process, which is inspired by these local properties of life dispersal on Earth. We split the population of stellar systems into different categories regarding habitability and evolved them through time using probabilistic cellular automata rules analogous to the model. As a dynamic effect, we include the existence of natural dispersal vectors (e.g. dust, asteroids) in a way that avoids assumptions about their agency (i.e. questions of existence). Moreover, by assuming that dispersal vectors have a finite velocity and range, the model includes the parameter of ‘optical depth of life spreading’. The effect of the oscillatory infection rate ($b( t,\; \, d)$) on the long-term behaviour of the dispersal flux, which adds a diffusive component to its progression, is also taken into account. The life recovery rate ($g( t,\; \, d)$) was only included in the model as a link to macrofaunal diversity data, which shows that all mass extinctions have a 10 Myr ‘speed rate’ in diversity recovery. This parameter accounts for the repopulation of empty viable niches as well as the formation of new ones, without ruling out the possibility of genuine life reemergence on other habitable worlds in the Galaxy that colossal extinctions have sterilized. All life-transmission events within the Galactic patch have thus been mapped into phase space characterized by parameters $b$ and $g$. We found that phase space is separated into subregions of long-lasting transmission, rapidly terminated transmission, and a transition region between the two. We observed that depending on the amplitude of the oscillatory life-spreading rate, life-transmission in the Galactic patch might take on different geometrical shapes (i.e. ‘waves’). Even if some host systems are uninhabited, life transmission has a certain threshold, allowing a patch to be saturated with viable material over a long period. Although stochastic fluctuations in the local density of habitable systems allow for clusters that can continuously infect one another, the spatial pattern disappears when life transmission is below the observed threshold, so that transmission process is not permanent in time. Both findings suggest that a habitable planet in a densely populated region may remain uninfected.

Genotypic variation and plasticity in climate-adaptive traits after range expansion and fragmentation of red spruce (Picea rubens Sarg.).

Shifting range limits are predicted for many species as the climate warms. However, the rapid pace of climate change will challenge the natural dispersal capacity of long-lived, sessile organisms such as forest trees. Adaptive responses of populations will, therefore, depend on levels of genetic variation and plasticity for climate-responsive traits, which likely vary across the range due to expansion history and current patterns of selection. Here, we study levels of genetic and plastic variation for phenology and growth traits in populations of red spruce (Picea rubens), from the range core to the highly fragmented trailing edge. We measured more than 5000 offspring sampled from three genetically distinct regions (core, margin and edge) grown in three common gardens replicated along a latitudinal gradient. Genetic variation in phenology and growth showed low to moderate heritability and differentiation among regions, suggesting some potential to respond to selection. Phenology traits were highly plastic, but this plasticity was generally neutral or maladaptive in the effect on growth, revealing a potential liability under warmer climates. These results suggest future climate adaptation will depend on the regional availability of genetic variation in red spruce and provide a resource for the design and management of assisted gene flow. This article is part of the theme issue 'Species' ranges in the face of changing environments (Part II)'.

Experimental Evaluation of the Driving Parameters in Human–Structure Interaction

Many studies in the literature have already evidenced that pedestrians are able to change the dynamic properties of slender structures (e.g., footbridges and staircases). The aim of this paper is to analyse which pedestrians’ features mostly affect the structure behaviour, in order to properly account for them in a human–structure interaction problem, while disregarding the less relevant ones. This is accomplished by measuring the apparent mass (i.e., the frequency response function between the vibration of the structure at the contact point and the consequent force exerted by the pedestrian to the structure itself) curves of human bodies and coupling them to the dynamics of a slender structure. In more detail, this paper aims at analysing which factors must be accounted for among intra-subject variability (i.e., the dynamic behaviour of the same subject can change because it is characterised by a natural dispersion), inter-subject variability (i.e., different subjects have different dynamic behaviours) and the posture (i.e., the same subject changes posture during motion and this causes a change of his/her dynamic features). The influence of the apparent mass properties on the modal parameters of the hosting structure is addressed by means of a modal approach.

Recovery in the melting pot: complex origins and restored genetic diversity in newly established Eurasian beaver (Rodentia: Castoridae) populations

Abstract Several larger vertebrate species have recovered from dramatic bottlenecks caused by overhunting and habitat destruction. One of the most notable comebacks concerns the Eurasian beaver (Castor fiber L.), which has increased its range by natural dispersal from both relict populations and populations established through translocations. Genetic methods have recently been used to study beavers at several locations. However, owing to a lack of reference samples from relict populations and alternative names of mitochondrial DNA haplotypes, the ancestry of re-established beaver populations remains obscure. Here, we focus on the genetic characterization of several newly established populations. Unlike previous studies, we also used microsatellite genotypes of reference samples from all relict populations. Our analysis was fully capable of tracing the origin of the nuclear and mitochondrial genome to relict populations. Although we confirmed an extraordinarily low genetic diversity in relict populations, our analysis showed restored diversity in newly established populations resulting from translocations. Recent expansions and stochastic effects have created a strong but complicated population structure, with neighbouring populations differing significantly in genetic composition. We conclude that this restored genetic diversity very likely contributes to the viability and ongoing expansion of the newly established populations.

Вплив людського фактору на бойову ефективність стрільби зі стрілецької зброї з оптичним прицілом

Розглянуто замкнений контур виконання бойової задачі із застосуванням стрілецької зброї з оптичним прицілом. Показано, що ймовірність виконання бойової задачі залежить не тільки від технічних характеристик зброї, боєприпасів тафоноцільової обстановки, але й від людського фактору. Оцінено ймовірність її виконання, враховуючи достовірність підготовки даних стрільби, виявлення, розпізнавання та ідентифікації цілі, вірного прицілювання і влучання при стрільбі.Для зменшення похибок стрільця при підготовці даних стрільби доцільно використовувати високоточні прилади вимірювання дальності і метеорологічну станцію. Похибки стрільця при прицілюванні суттєво зменшуються при систематичному тренуванні на спеціальному стенді з електронною мішенню. Для скорочення часу при пошуку цілі на великій відстані доцільно використовувати телескопічний приціл. Для підвищення ймовірності розпізнавання та ідентифікації цілі доцільні тренування на спеціальному стенді, на якому імітується різноманітна фоноцільова обстановка.

EU-Trees4F, a dataset on the future distribution of European tree species

We present “EU-Trees4F”, a dataset of current and future potential distributions of 67 tree species in Europe at 10 km spatial resolution. We provide both climatically suitable future areas of occupancy and the future distribution expected under a scenario of natural dispersal for two emission scenarios (RCP 4.5 and RCP 8.5) and three time steps (2035, 2065, and 2095). Also, we provide a version of the dataset where tree ranges are limited by future land use. These data-driven projections were made using an ensemble species distribution model calibrated using EU-Forest, a comprehensive dataset of tree species occurrences for Europe, and driven by seven bioclimatic parameters derived from EURO-CORDEX regional climate model simulations, and two soil parameters. “EU-Trees4F”, can benefit various research fields, including forestry, biodiversity, ecosystem services, and bio-economy. Possible applications include the calibration or benchmarking of dynamic vegetation models, or informing forest adaptation strategies based on assisted tree migration. Given the multiple European policy initiatives related to forests, this dataset represents a timely and valuable resource to support policymaking.

The reconstruction of invasion histories with genomic data in light of differing levels of anthropogenic transport.

Unravelling the history of range shifts is key for understanding past, current and future species distributions. Anthropogenic transport of species alters natural dispersal patterns and directly affects population connectivity. Studies have suggested that high levels of anthropogenic transport homogenize patterns of genetic differentiation and blur colonization pathways. However, empirical evidence of these effects remains elusive. We compared two range-shifting species (Microcosmus squamiger and Ciona robusta) to examine how anthropogenic transport affects our ability to reconstruct colonization pathways using genomic data. We first investigated shipping networks from the 18th century onwards, cross-referencing these with regions where the species have records to infer how each species has potentially been affected by different levels of anthropogenic transport. We then genotyped thousands of single-nucleotide polymorphisms from 280 M. squamiger and 190 C. robusta individuals collected across their extensive species' ranges and reconstructed colonization pathways. Differing levels of anthropogenic transport did not preclude the elucidation of population structure, though specific inferences of colonization pathways were difficult to discern in some of the considered scenario sets. We conclude that genomic data in combination with information of underlying introduction drivers provide key insights into the historic spread of range-shifting species.This article is part of the theme issue ‘Species’ ranges in the face of changing environments (part I)’.

Development of new computational machine learning models for longitudinal dispersion coefficient determination: case study of natural streams, United States.

Natural streams longitudinal dispersion coefficient (Kx) is an essential indicator for pollutants transport and its determination is very important. Kx is influenced by several parameters, including river hydraulic geometry, sediment properties, and other morphological characteristics, and thus its calculation is a highly complex engineering problem. In this research, three relatively explored machine learning (ML) models, including Random Forest (RF), Gradient Boosting Decision Tree (GTB), and XGboost-Grid, were proposed for the Kx determination. The modeling scheme on building the prediction matrix was adopted from the well-established literature. Several input combinations were tested for better predictability performance for the Kx. The modeling performance was tested based on the data division for the training and testing (70-30% and 80-20%). Based on the attained modeling results, XGboost-Grid reported the best prediction results over the training and testing phase compared to RF and GTB models. The development of the newly established machine learning model revealed an excellent computed-aided technology for the Kx simulation.

JESIOTR WSCHODNI ACIPENSER GUELDENSTAEDTII BRANDT & RATZEBURG, 1833 (ACTINOPTERYGII, ACIPENSERIDAE) W RZECE EUFRAT, IRAK

Acipenser gueldenstaedtii is recorded for the first time from the Euphrates River, west of Iraq. The species has not previously been mentioned as introduced to the Tigris-Euphrates River basin. There are two possibilities for this occurrence, first, the natural dispersal from adjacent Turkey and second, the aquaculture introduction. Both possibilities were discussed. Confirmation for the origin of the sporadic appearance of individuals of this species will wait for the appearance of more specimens in the inland waters of Iraq.

Genetic Patterns of Zamia in Florida Are Consistent with Ancient Human Influence and Recent Near Extirpation

Premise of research. The only cycad native to the continental United States, Zamia integrifolia, is a taxonomically controversial species with a long history of use by people culminating in near extirpation 100 yr ago. We sought to illuminate the geographic and morphological variation in these plants, to inform the conservation of this threatened species, and to investigate hypotheses about human-mediated dispersal using molecular genetic data.Methodology. We genotyped 25 populations from the Florida peninsula with 26 microsatellite (simple sequence repeat) loci and analyzed the data with neighbor-joining and multivariate analysis of genetic distance, Bayesian clustering, and network analyses.Pivotal results. Patterns of genetic diversity are congruent with patterns of morphology and geography. Populations from northeast Florida that correspond to Z. integrifolia var. umbrosa are genetically distinct and cohesive. Overall, the genetic diversity of Florida’s Zamia is reduced relative to that of closely related populations in the Caribbean, consistent with the history of commercial exploitation and the recent geological history of the Florida peninsula.Conclusions. We offer specific management recommendations based on these data. We recognize only two varieties of the species in Florida: var. integrifolia and var. umbrosa. Patterns of genetic and geographic diversity are closely consistent with interaction networks of Woodland period (1000 BC to 1000 AD) Native Peoples and are not consistent with natural dispersal dynamics. This suggests that human-mediated dispersal played a role in the current distribution and diversity of the species.

Spatial distribution and fluctuating populations of predatory mites (Mesostigmata: Phytoseiidae), phytophagous mites (Acari: Eriophyidae, Tetranychidae) and their relationships with wild chili pepper phenological stages in two Natural Protected Areas of Mexico

Ecological interactions between mites (predatory and phytophagous) and wild plants growing in undisturbed environments play a crucial role to understand their natural settlement, development and dispersion patterns. Pequin chili pepper, Capsicum annuum L. var. glabriusculum, is a low-cost natural resource for local communities living inside Natural Protected Areas (ANP) of Tamaulipas State in Mexico. The aims of this research work were: 1) determine the spatial distribution pattern of predatory and phytophagous mites, 2) determine the spatiotemporal association between predatory and phytophagous mites, and 3) determine the association among different mite species and some phenological stages of Pequin chili pepper. The most abundant phytophagous mites were Tetranychus merganser and Aculops lycpoersici, and the predatory species were Amblyseius similoides, Euseius mesembrinus and Metaseiulus (Metaseiulus) negundinis. Most mite species showed an aggregated distribution pattern according to the plant phenological stages. However, the distribution of mite species throughout time showed different types of aggregation. On the other hand, we found positive associations among A. lycopersici and T. merganser phytophagous mites with A. similoides, E. mesembrinus and M. (M.) negundinis predators mites. The association between plants and mite species were influenced by the phenological stages of Pequin chili pepper. This is an indication of the complexity among trophic-chain interactions that depend largely on the available resources and competition. These two factors serve as foundations for settlement, development and dispersion patterns of certain species.

Secondary Seed Ingestion in Snakes: Germination Frequency and Rate, Seedling Viability, and Implications for Dispersal in Nature

The importance of vertebrate animals as seed dispersers (zoochory) has received increasing attention from researchers over the past 20 years, yet one category in particular, diploendozoochory, remains understudied. As the term implies, this is a two-phase seed dispersal system whereby a secondary seed predator (carnivorous vertebrate) consumes a primary seed predator or granivore (rodent and bird) with undamaged seeds in their digestive tract (mouth, cheek pouch, crop, stomach, or other organ), which are subsequently eliminated with feces. Surprisingly, although snakes are among the most abundant predators of granivorous vertebrates, they are the least studied group insofar as our knowledge of seed rescue and secondary dispersal in a diploendozoochorous system. Here, using live snake subjects of the Sonoran Desert (one viperid and two colubrid species) and seeds of the Foothill Palo Verde (Parkinsonia microphylla), a dominant tree of the same region, we experimentally tested germination frequency and rate, and seedling viability. Specifically, to mimic rodents with seed-laden cheek pouches, we tested whether wild-collected P. microphylla seeds placed in the abdomen of thawed laboratory mice and ingested by the snakes would retain their germination viability. Second, we examined whether seeds exposed to gut transit germinated at a greater frequency and rate than the controls. While we found strong statistical support for our first hypothesis, both aspects of the second one were not significant. Accordingly, we provide an explanation for these results based on specific life-history traits (dormant and non-dormant seeds) of P. microphylla. Our study provides support for the role of snakes as important agents of seed rescue and dispersal in nature, their potential as ecosystem engineers, and crucial evidence for the investment of field-based studies on diploendozoochorous systems in deserts and other ecosystems.