Decline In Richness Research Articles

Seaweed functional strategies, functional groups, and taxon dynamics through a 213-year historical series of Rio De Janeiro Bay

From Darwin’s visit to nowadays, we analyzed the changes in species- and genus-level richness and turnover, equity, diversity, composition, as well as functional group and functional strategy dynamics over a 213-year historical series of the seaweed assemblage from Rio de Janeiro Bay. We developed new analysis methods to serve as a protocol for worldwide functional and bioindicator assessment of seaweed assemblages. Over the two centuries of changes tracked, the integration of taxonomic, functional group, and functional strategy analyses unraveled a trajectory of seaweed assemblage restructuring under human disturbance. Our taxonomic analyses showed a high species and genus turnover and a decline in richness, with the local extinction of the Sargassum genus, responsible for warm temperate kelp forests in the Western Atlantic. Seaweed functional group data presented a trend of morphological simplification and miniaturization, with the decline of marine forest canopy and subcanopy-forming groups favoring filamentous and crustose algae dominance. Functional strategy data showed the historical decline of competitive structuring as an assemblage driver in favor of disturbance and stress-structuring, as highlighted by the competitive strategy decrease, coupled with stress-tolerant and ruderal strategies rise across metrics. These changes were successfully portrayed by the new ecological index we proposed, the C/SR index. It is the first quantitative index for seaweed assemblages, designed to be a trackable metric for conservation, monitoring, and restoration efforts.

Rapid declines in freshwater gastropods in Pune city, India

ABSTRACT We studied freshwater gastropod fauna in a heavily urbanized region in tropical India, across a range of habitat types. A total of 16 species were found from a two-year survey, which is a decline of 27% compared to studies completed in the 1970s. Planorbidae was the most species rich family in the collection, with five species. Racesina luteola (Lamarck, 1822) was the most commonly occurring species in the collection. Three non-native species, including Pomacea diffusa (Blume, 1957), are also reported. Habitat type influenced species occurrences, although lentic and lotic habitats were largely similar in their fauna. Many species reported previously were missing from the current survey, along with an increased incidence of non-native species which were absent from earlier reports. This decline in species richness, particularly of native species, alongside an increased incidence and spread of non-native species in the region, highlights the impact of urbanization on the freshwater gastropod community.

Recent Sociocultural Changes Reverse the Long‐Term Trend of Declining Habitat Availability for Large Wild Mammals in Europe

ABSTRACTAimPeople have strongly influenced the biosphere for millennia, but how their increasing activities have shaped wildlife distribution is incompletely understood. We examined how the distribution of European large (>8 kg), wild mammals has changed in association with changing anthropogenic pressures and climate change through the Holocene.LocationEurope.MethodsWe used over 17,000 zooarchaeological records of 20 species spanning 12,000 years to develop time‐calibrated species distribution models, incorporating dynamic data on cropland extent, natural vegetation fragmentation, human population density and climate. We assessed habitat availability and potential species richness across time and within seven biogeographical regions. We also compared anthropogenic pressures at zooarchaeological record sites with present‐day habitats of remaining large mammals to evaluate recent increases in their potential for coexistence with human activities.ResultsWe found a continuous decline in potential large mammal species richness, particularly linked to changes in human population density. Most habitat loss became evident continentally after 1500 AD, but in the Atlantic and Mediterranean bioregions, habitat loss reached 20% during the Iron/Roman Ages (1000 BC–500 AD) due to increasing human population density. Climate change initially boosted species richness (+0.67 species/km2 on average) until the end of the Mesolithic but had negligible effects afterward. Today, large mammals appear to have a higher potential for coexisting with people compared to the past (e.g., herbivores today inhabit areas with a mean human population density of 95 people/km2, compared to an average of 17 people/km2 in the period 1500–2000 AD).Main ConclusionsOur study emphasizes the crucial role of anthropogenic pressures over natural climate change in determining the distribution and diversity of large mammal communities throughout history. Additionally, our results indicate that contemporary anthropogenic trends like land‐use de‐intensification and stronger conservation policies can counteract the impact of past, higher anthropogenic pressures and reverse defaunation.

Understory plant biodiversity is inversely related to carbon storage in a high carbon ecosystem.

Given that terrestrial ecosystems globally are facing the loss of biodiversity from land use conversion, invasive species, and climate change, effective management requires a better understanding of the drivers and correlates of biodiversity. Increasingly, biodiversity is co-managed with aboveground carbon storage because high biodiversity in animal species is observed to correlate with high aboveground carbon storage. Most previous investigations into the relationship of biodiversity and carbon co-management do not focus on the biodiversity of the species rich plant kingdom, which may have tradeoffs with carbon storage. To examine the relationships of plant species richness with aboveground tree biomass carbon storage, we used a series of generalized linear models with understory plant species richness and diversity data from the USDA Forest Service Forest Inventory and Analysis dataset and high-resolution modeled carbon maps for the Tongass National Forest. Functional trait data from the TRY database was used to understand the potential mechanisms that drive the response of understory plants. Understory species richness and community weighted mean leaf dry matter content decreased along an increasing gradient of tree biomass carbon storage, but understory diversity, community weighted mean specific leaf area, and plant height at maturity did not. Leaf dry matter content had little variance at the community level. The decline of understory plant species richness but not diversity to increases in aboveground biomass carbon storage suggests that rare species are excluded in aboveground biomass carbon dense areas. These decreases in understory species richness reflect a tradeoff between the understory plant community and aboveground carbon storage. The mechanisms that are associated with observed plant communities along a gradient of biomass carbon storage in this forest suggest that slower-growing plant strategies are less effective in the presence of high biomass carbon dense trees in the overstory.

Species Richness and Similarity of New Zealand Mayfly Communities (Ephemeroptera) Decline with Increasing Latitude and Altitude.

The distribution of species in relation to latitude and altitude is of fundamental interest to ecologists and is expected to attain increasing importance as the Earth's climate continues to change. Species diversity is commonly greater at lower than higher latitudes on a global scale, and the similarity of communities frequently decreases with distance. Nevertheless, reasons for such patterns are not well understood. We investigated species richness and changes in community composition of mayflies (Ephemeroptera) over 13 degrees of latitude at 81 locations throughout New Zealand by light-trapping and the benthic sampling of streams. Mayflies were also sampled along an altitudinal gradient on a prominent inactive volcano in the east of North Island. Sampled streams were predominantly in the native forest, at a wide range of altitudes from sea level to c. 1000 m a. s. l. A total of 47 of the 59 described New Zealand mayflies were recorded during the study, along with five undescribed morphospecies. Species richness declined and the degree of dissimilarity (beta diversity) of mayfly communities increased significantly from north to south but less strongly with increasing altitude. Our results suggest that the southward decline in species richness has historical origins with the north of the country having acted as a major refuge and region of speciation during the Pleistocene. The increasing dissimilarity of the northern and southern communities may reflect an increasingly harsh climate, variable amounts of subsequent southward dispersal of northern species and, in the South Island, the presence of species which may have evolved in the newly uplifted mountains during the Miocene-Pliocene.

Redistribution of vocal snapping shrimps under climate change

A variety of marine organisms can produce sounds that are important components of the marine soundscape and play a critical role in maintaining marine biodiversity. Climate change has greatly altered the geographical ranges of many marine species, including sound-producing organisms. However, the direction and the magnitude of the potential impact of climate change on the geographical distribution of sound-producing marine organisms in future remain largely unknown. To address this knowledge gap, we selected snapping shrimp, one of the most well-known marine sound-producing organisms, as a model species and explored their redistribution under climate change via species distribution models. We aimed to predict the redistribution of snapping shrimps under climate change and identify the influencing factors, which have important implications for marine conservation. Our models exhibited good discrimination abilities and identified maximum temperature as the most influential predictor of snapping shrimp distribution. Model predictions suggested that species richness is higher in tropical and temperate coastal waters and peaks in the Indo-Pacific region. The majority of snapping shrimp species are expected to respond to the changing climate by shifting their geographical ranges to deeper waters and higher latitudes. Our results showed that, in the future, high-latitude species were more likely to experience range expansion, whereas low-latitude species might experience range contraction. Moreover, the Central Indo-Pacific are predicted to suffer the biggest decline in species richness, whereas areas such as the coastal waters of southern Australia and northern China might serve as climate refuges for snapping shrimps in the future. In summary, this study highlights the potential effects of climate change on the distribution of sound-producing snapping shrimps, which may result in cascading effects on marine ecosystems.

Global analysis of soil bacterial genera and diversity in response to pH

Soil pH stands as a decisive factor in shaping bacterial diversity and community composition, yet predicting the pH preferences and traits of individual bacterial taxa is still incomplete. We surveyed 942 samples from seven biomes worldwide to unravel the responses of individual bacterial genus to soil pH. Our findings indicate that soil pH surpasses the influences of spatial and climatic factors (biomes) in affecting bacterial composition and diversity. We observed that a comparable proportion of genera had low pH optima (21%), high pH optima (18%), and neutral pH optima (18%). However, apart from genera with optima groups, only a small percentage of genera were low pH tolerant (0.8%) compared to those that were high pH tolerant (21%). This suggests that a greater number of non-extremophiles genera can tolerate alkaline conditions compared to acidic conditions. Bacterial richness forms unimodal relationship with soil pH, consistently increasing from acidic levels to neutral across all biomes. However, the decline in richness when pH rises beyond neutral was less pronounced. This can be attributed to the higher number of alkaline-tolerant genera compared to acidic-tolerant genera. As expected, genera with acidic optima are more prevalent in humid climates, such as tropical forests, arctic tundra, and boreal forests, whereas genera with alkaline optima are generally dominant in arid grasslands and drylands. Collectively, our results indicate that the probability of existence of at least 75% of genera in specific soil pH conditions can be predicted, irrespective of biome. The identification of the actual niche spaces occupied by individual soil bacterial genera forms the foundation for developing comprehensive hypotheses regarding the response of soil communities to changing soil conditions worldwide.

An Approach to Assessing the Impact of Hurricane Matthew on Meiofaunal Communities in Sandy Beach Environments

ABSTRACTHurricanes are natural periodic events that disrupt marine ecosystems along their path, altering the distribution and abundance of organisms. In October 2016, Hurricane Matthew struck the Santa Marta region (Colombia) and impacted its coastal zone, yet there have been insufficient studies to measure its effects. The aim of this study was to assess the impact of Hurricane Matthew on the meiofaunal community in the region. To achieve this, sediment samples were collected from the intertidal zone of three beaches 5 days after the hurricane had passed. The results were compared with previous data collected in October 2014, on the abundance and diversity of taxonomic groups of intertidal meiofauna, as well as physicochemical variables such as granulometry, organic matter in sediments, salinity, and water temperature. Following Hurricane Matthew, the physicochemical variables showed changes due to the effect of the cyclonic surge in the coastal zone. The average organism abundance not only experienced a decline in both abundance and richness but also underwent changes in composition. Nematoda, originally the fourth most abundant group in 2014, became the most dominant taxon post‐hurricane. Conversely, the relative abundance of Copepoda decreased. The total number of recorded taxa was 13, which is close to the 15 previously reported. The ANOSIM and PERMANOVA tests confirmed differences in the meiofaunal community before and after Hurricane Matthew, with Tardigrada, Cnidaria, Ostracoda and Mollusca, being the main groups that contributed the most to the dissimilarity between periods. The environmental variables of organic matter and temperature best explained the structure of the meiofaunal community after the natural phenomenon. This study highlights the importance of meiofauna as a monitoring tool for beaches and the effects of environmental disturbances such as hurricanes, which are expected to become more common in coastal areas due to climate change.

Temporal microbiome changes in axolotl limb regeneration: Stage-specific restructuring of bacterial and fungal communities with a Flavobacterium bloom during blastema proliferation.

The intricate relationship between regeneration and microbiota has recently gained attention, spanning diverse model organisms. Axolotl (Ambystoma mexicanum) is a critically endangered salamander species and a model organism for regenerative and developmental biology. Despite its significance, a noticeable gap exists in understanding the interplay between axolotl regeneration and its microbiome. Here, we analyse in depth bacterial 16S rRNA amplicon dataset that we reported before as data resource and profile fungal community by sequencing ITS amplicons at the critical stages of limb regeneration (0-1-4-7-30-60 days post amputation, 'dpa'). Results reveal a decline in richness and evenness in the course of limb regeneration, with bacterial community richness recovering beyond 30 dpa unlike fungi community. Beta diversity analysis reveals precise restructuring of the bacterial community along the three phases of limb regeneration, contrasting with less congruent changes in the fungal community. Temporal dynamics of the bacterial community highlight prevalent anaerobic bacteria in initiation phase and Flavobacterium bloom in the early phase correlating with limb blastema proliferation. Predicted functional analysis mirrors these shifts, emphasising a transition from amino acid metabolism to lipid metabolism control. Fungal communities shift from Blastomycota to Ascomycota dominance in the late regeneration stage. Our findings provide ecologically relevant insights into stage specific role of microbiome contributions to axolotl limb regeneration.

Environmental preferences of soil microbial attributes for long-term nitrogen and acid addition: From phylotype to community

The impact of human-induced nitrogen (N) enrichment on microbial diversity has been extensively studied, with two main hypotheses proposed: soil N availability and soil acidification. However, the specific roles of these two hypotheses and their environmental preferences on soil bacterial and fungal communities are not fully understood. By conducting two independent experiments (a 16-year N and a 6-year acid addition) in a temperate semi-arid grassland, we tested the responses of soil microbial attributes (e.g., richness and relative abundance) at various levels (community, phylum/class, and phylotype) to N and acid addition. At the community level, our results showed that both N and acid addition had a negative effect on the richness of the whole, dominant, and rare bacterial communities; N enrichment only decreased the richness of the dominant fungal community, while acid addition decreased the richness of the whole, dominant, and rare fungal communities. By categorizing the microbial attributes into nine environmental preferences based on their responses to N and acid addition, we found that most bacterial phyla were associated with low N availability and high pH preferences, while most fungal classes had other environmental preferences. Most dominant bacterial phylotypes were linked to low N availability and high pH preferences, while most dominant fungal phylotypes were associated with other environmental preferences and high pH preferences. Conversely, most rare bacterial and fungal phylotypes were linked to other environmental preferences. Our experiments revealed that the decline in bacterial richness caused by N enrichment was predominantly due to their sensitivity to soil acidification, while fungal richness remained largely unaltered. By pinpointing distinct microbial attributes at different levels in response to N and acid addition, our findings could potentially forecast how soil microorganisms will react to future global N deposition.

Post-Burn, Post-Flood Effects In A Degraded Grassland, Lake Texoma, Bryan County, Oklahoma

Plant communities change over time, sometimes leading to an increase or decrease in biological diversity. Often, absence of active management of a site leads to its degradation including loss of native species and invasion by non-native weeds. Lake Texoma, Texas and Oklahoma, represents an area where extensive landscape change has happened over the course of almost a century. The Denison Dam was completed in 1938, forming the lake, which over time has altered conditions in the forested and formerly-grazed locations surrounding it. The location studied in this paper is a 186-ha tract of land situated between Johnson Creek and the Roosevelt Bridge in Bryan County, Oklahoma. In summer 2000, a species list was compiled for a grassland located at the lake site as part of a larger study. This grassland comprised ~10% of the total site area. Following two major floods and an extended drought, the site was resampled in 2018. Results indicated it had suffered a serious decline in species richness and an increase in abundance of invasive or encroaching species. Species richness was reduced by approximately 50% between 2000 and 2018. Fewer transects were sampled in 2018 because of woody encroachment on the original site. In spring 2021, following an extensive prescribed burn, the site was resampled to see if burning led to any reduction in undesirable species. The most frequent species in 2000 included Panicum philadelphicum, Lespedeza virginica, Rudbeckia hirta and Ambrosia psilostachya and in 2018 they were Lespedeza cuneata, Ambrosia psilostachya, and Dichanthelium oligosanthes. It is possible that the invasive Lespedeza cuneata (sericea lespedeza) spread after a 2007 flood because of some combination of reduced competition and transport of seed in floodwater. In 2021, the most frequent species were the same as in 2018, showing little effect of the burn. However, the Shannon diversity and evenness in both early and late summer sampling periods after the burn were higher than those for the 2018 data, suggesting that the burn may have had some effect. To attempt to restore the site to more “native” conditions would probably require some combination of regular burning, flash grazing, and possibly herbicide use. Once sericea lespedeza establishes, it is very difficult to eradicate from a location.

Long term declines in the functional diversity of sharks in the coastal oceans of eastern Australia

Human impacts lead to widespread changes in the abundance, diversity and traits of shark assemblages, altering the functioning of coastal ecosystems. The functional consequences of shark declines are often poorly understood due to the absence of empirical data describing long-term change. We use data from the Queensland Shark Control Program in eastern Australia, which has deployed mesh nets and baited hooks across 80 beaches using standardised methodologies since 1962. We illustrate consistent declines in shark functional richness quantified using both ecological (e.g., feeding, habitat and movement) and morphological (e.g., size, morphology) traits, and this corresponds with declining ecological functioning. We demonstrate a community shift from targeted apex sharks to a greater functional richness of non-target species. Declines in apex shark functional richness and corresponding changes in non-target species may lead to an anthropogenically induced trophic cascade. We suggest that repairing diminished shark populations is crucial for the stability of coastal ecosystems.

Bioclimatic and remote sensing factors are better key indicators than local topography and soil: Vegetation composition variability in forests of Pakistan's Spin Ghar Mountain range

The composition, structure and distribution of vegetation are influenced by diverse environmental factors. Such research inquiries provide the initial data for future conservation and management efforts. The study area of North Waziristan district, Khyber Pakhtunkhwa, Pakistan comprises diverse forests of the Spin Ghar Mountain Range (at the border areas of Pakistan and Afghanistan), and a highly remote, mountainous, and unexplored region. There was little information on the complex relationships that existed between the study area's ambient environment and vegetation. This study hypothesized that the varying environmental complexity in the study area and vegetation variety may be significantly correlated, and the ranking of leading influencing factors might enhance our ecological understanding. A total of 61 study sites comprising 183 transects (50 m each) were randomly selected to record the vegetation-environment data from January-2018 to December-2020 (3 years). Monte Carlo permutation testing, hierarchical clustering of study samples, indicator species analysis, and ordination were applied to assess the sampling data. The results indicated that there were a total of 391 vascular plant species which were further classified into seven significantly different (p < 0.05) plant assemblages, each comprising of a distinct species makeup. A variety of different environmental variables (topographic (06), bioclimatic (19), edaphic (09), remote sensing, and anthropogenic predictors (16)) were considered. Simple term effects testing results depicted the significant (p(adj) < 0.05) role of 39 variables initially, whereas, conditional term effects testing (with variance inflation factor (VIF) threshold value of < 10, and forward selecting variables that provided the most unique information) results highlighted the prominent role of eight (08) contributors. The results of the latter analysis ranked the mean temperature of the warmest quarter (Bio10) as the most influencing factor, followed by Normalized Difference Vegetation Index (NDVI), longitude, continuous heat insulation load index (CHILI), precipitation of the warmest quarter (Bio18), global human modification of the terrestrial systems (gHM), organic carbon density (OCD), and annual precipitation (Bio12). This study concluded that the vegetation variability in the study area was significantly correlated with the prevailing environment, and considered bioclimatic and remote sensing factors were better key indicators for any vegetation distribution when the study was conducted on a large spatial scale. Based on these results, the anticipated future variations in climate, particularly global warming, lengthy drought spells, and population explosion might remarkably lead to decline in local plant species richness and distribution. For the study area to guard its priceless biodiversity for future generations, careful and prompt conservation and management planning are required.

Vegetation dieback in the Mississippi River Delta triggered by acute drought and chronic relative sea-level rise

Vegetation dieback and recovery may be dependent on the interplay between infrequent acute disturbances and underlying chronic stresses. Coastal wetlands are vulnerable to the chronic stress of sea-level rise, which may affect their susceptibility to acute disturbance events. Here, we show that a large-scale vegetation dieback in the Mississippi River Delta was precipitated by salt-water incursion during an extreme drought in the summer of 2012 and was most severe in areas exposed to greater flooding. Using 16 years of data (2007–2022) from a coastwide network of monitoring stations, we show that the impacts of the dieback lasted five years and that recovery was only partial in areas exposed to greater inundation. Dieback marshes experienced an increase in percent time flooded from 43% in 2007 to 75% in 2022 and a decline in vegetation cover and species richness over the same period. Thus, while drought-induced high salinities and soil saturation triggered a significant dieback event, the chronic increase in inundation is causing a longer-term decline in cover, more widespread losses, and reduced capacity to recover from acute stressors. Overall, our findings point to the importance of mitigating the underlying stresses to foster resilience to both acute and persistent causes of vegetation loss.

Short-Interval, High-Severity Wildfire Depletes Diversity of Both Extant Vegetation and Soil Seed Banks in Fire-Tolerant Eucalypt Forests

Many plant species are well-adapted to historical fire regimes. An increase in the severity, frequency, and extent of wildfires could compromise the regenerative capacity of species, resulting in permanent shifts in plant diversity. We surveyed extant vegetation and soil seed banks across two forest types with contrasting historical fire regimes—Shrubby Dry Forest (fire return interval: 10–20 years) and Sub-Alpine Woodland (50–100 years). Over the past 20 years, both forests have been subject to repeated, high-severity wildfires at intervals significantly shorter than their historical return intervals. We examined the soil seed bank response to fire-cued germination, and whether the plant diversity in soil seed banks and extant vegetation demonstrated similar responses to short-interval, high-severity wildfires. The soil seed bank demonstrated a positive response to heat in combination with smoke, and for the Sub-Alpine Woodland, this was limited to sites more frequently burnt by fire. With an increase in fire frequency, there was a decline in species richness and Shannon’s Diversity and a shift in species composition in both extant vegetation and the soil seed bank. The fire frequency effects on the relative richness of trait associations were restricted to the Shrubby Dry Forest, and included an increase in short-lived obligate seeders, wind-dispersed species, and ant-dispersed shrubs in burnt relative to long unburnt sites in both extant vegetation and the soil seed bank. Graminoids were the most abundant component of the soil seed banks of Sub-Alpine Woodlands, and this increased with more frequent fire, with a similar trend (p = 0.06) in extant vegetation. Clear shifts in plant diversity in both soil seed banks and extant vegetation in forest types with contrasting historical fire regimes suggest that emerging fire regimes are pushing ecosystems beyond their historical range of variability, including potentially more flammable states and a decline in the buffering capacity of soil seed banks.

Revealing hidden diversity and community dynamics of land snails through DNA barcoding: implications for conservation and ecological studies

IntroductionLand snails play a crucial role in maintaining ecosystem sustainability within their habitats. Therefore, understanding the characteristics of their communities is vital for ecological studies and the development of effective conservation strategies. In this study, land snail communities inhabiting the Hyrcanian forest were identified and the variations in their community composition along elevational gradients were investigated.MethodsSnail samples were collected from three distinct elevations in three different forest locations within the Hyrcanian area of Iran. This study utilized DNA barcoding to identify land snail species. By employing statistical analyses such as ANOVA and PERMANOVA, significant differences in the features of snail communities across different elevations were examined. Concurrently, soil samples were collected from each site to assess soil physicochemical parameters about snail presence.ResultThrough this comprehensive analysis, a total of 10 OTUs, were further classified into seven families, and nine genera were identified. Five of these genera had never been reported in the study region before. We observed a decline in OTU richness with increasing elevation; however, the maximum abundance of snails was found at higher elevations. CCA demonstrated that Ca, Mg, and moisture saturation predominantly shape snail community composition.DiscussionThe unique climatic conditions and spatial distribution of precipitation from lowlands to highlands, as well as from west to east, make the Hyrcanian forests an ideal case study area for understanding the dynamics of land snail communities. In summary, this study provides new insights into the land snail communities thriving in the Hyrcanian forests. The findings from our research can contribute to the development of effective conservation management strategies for forest ecosystems. By understanding the factors influencing the distribution and composition of land snail communities, we can make informed decisions to protect and preserve land snails and the balance they maintain within their habitats.

Resistance not resilience traits structure macroinvertebrate communities in newly drying stream sections

Transitioning from perennial to non-perennial flow regimes causes ecological shifts in aquatic communities. Aquatic macroinvertebrates deploy resistance and resilience strategies to cope with flow intermittency, crucial in rivers with long-term seasonal dry episodes. Less is known, about how these strategies support community persistence in streams that only recently have experienced drying, and where local assemblages lack such adaptations. Our study conducted two four-season campaigns, separated by a one-year break, to assess macroinvertebrate responses in newly drying intermittent streams by comparing intermittent and perennial stream sections. We characterize communities from structural and functional perspectives, and then evaluate the response at the trait state level. We observed a decline in taxa richness and abundance, but not structural diversity, in response to flow intermittency. Resistance traits are more important than resilient traits in structuring macroinvertebrate communities in newly intermittent stream sections. Taxa in intermittent sections exhibit a smaller trait space, indicating lower functional redundancy. The macroinvertebrate response to intermittency lacks a predictable pattern, suggesting time-dependent and trait-state-specific colonization by adapted taxa and community assembly with resistance and resilience strategies. As river drought increases due to climate change, recognizing the temporal dimension becomes crucial for understanding ecological responses to intermittency.

Identification of temporal shifts of oral bacteria in bone regeneration following mandibular bone defect injury and therapeutic surgery in a porcine model.

Considered the second largest and most diverse microbiome after the gut, the human oral ecosystem is complex with diverse and niche-specific microorganisms. Although evidence is growing for the importance of oral microbiome in supporting a healthy immune system and preventing local and systemic infections, the influence of craniomaxillofacial (CMF) trauma and routine reconstructive surgical treatments on community structure and function of oral resident microbes remains unknown. CMF injuries affect a large number of people, needing extensive rehabilitation with lasting morbidity and loss of human productivity. Treatment efficacy can be complicated by the overgrowth of opportunistic commensals or multidrug-resistant pathogens in the oral ecosystem due to weakened host immune function and reduced colonization resistance in a dysbiotic oral microbiome. To understand the dynamics of microbiota's community structure during CMF injury and subsequent treatments, we induced supra-alveolar mandibular defect in Hanford miniature swine (n=3) and compared therapeutic approaches of immediate mandibullar reconstructive (IMR) versus delayed mandibullar reconstructive (DMR) surgeries. Using bacterial 16S ribosomal RNA gene marker sequencing, the composition and abundance of the bacterial community of the uninjured maxilla (control) and the injured left mandibula (lingual and buccal) treated by DMR were surveyed up to 70-day post-wounding. For the injured right mandibula receiving IMR treatment, the microbial composition and abundance were surveyed up to 14-day post-wounding. Moreover, we measured sera level of biochemical markers (e.g., osteocalcin) associated with bone regeneration and healing. Computed tomography was used to measure and compare mandibular bone characteristics such as trabecular thickness between sites receiving DMR and IMR therapeutic approaches until day 140, the end of study period. Independent of IMR versus DMR therapy, we observed similar dysbiosis and shifts of the mucosal bacteria residents after CMF injury and/or following treatment. There was an enrichment of Fusobacterium, Porphyromonadaceae, and Bacteroidales accompanied by a decline in Pasteurellaceae, Moraxella, and Neisseria relative abundance in days allotted for healing. We also observed a decline in species richness and abundance driven by reduction in temporal instability and inter-animal heterogeneity on days 0 and 56, with day 0 corresponding to injury in DMR group and day 56 corresponding to delayed treatment for DMR or injury and immediate treatment for the IMR group. Analysis of bone healing features showed comparable bone-healing profiles for IMR vs. DMR therapeutic approach.

Habitat fragmentation erodes taxonomic and functional diversity of waterbird communities of the South Pacific coast of Mexico

We characterize the taxonomic and functional diversity of waterbird communities in mangrove forests of 23 coastal lagoons in the southern Mexican Pacific coast, to evaluate the hypothesis of decline of taxonomic and functional richness of waterbird communities in the face of loss of natural habitat cover and increased fragmentation. We quantified patterns of land use cover, considering the heterogeneity of natural and anthropized vegetation cover as a proxy for human-caused fragmentation, and used generalized linear models to explore the relationship between these two covers with the taxonomic richness and functional richness of bird communities. Results show that both aspects of biodiversity positively relate to larger natural habitat areas, while higher fragmentation values have a negative effect on them. Our results suggest that habitat loss and fragmentation of vegetation cover negatively affect the diversity of waterbird communities and can compromise their link to ecosystem functioning processes in coastal lagoons, by decreasing their functional diversity.

Sampling through space and time: multi-year analysis reveals dynamic population genetic patterns for an amphibian metapopulation

Metapopulations are dynamic, and population genetics can reveal both spatial and temporal metapopulation variation. Yet, population genetic studies often focus on samples collected within a single time period or combine samples taken across time periods due to limited resources and the assumption that these approaches capture patterns and processes occurring over decadal and longer temporal scales. However, this may leave important fine-scale temporal variation in genetic composition undetected, particularly for metapopulations in which dynamic populations are expected. We investigated temporal patterns of population genetic diversity, effective population size, and differentiation across three sample periods for a dryland amphibian metapopulation. We sampled nine distinct Arizona treefrog (Hyla (Dryophytes) wrightorum) breeding ponds in 2014, 2018/2019, and 2021 and genotyped 17 microsatellite loci to quantify spatial and temporal population genetic dynamics. Genetic diversity within and between populations varied significantly among years. Most notably, we identified a concerning decline in allelic richness across populations, with an average − 26.11% difference between a population’s first and last sample period. Effective population sizes were generally small (Ne < 100) and variable within and among populations over time, with many populations falling below common conservation thresholds by the final sample period. Trends in global genetic diversity, as measured by heterozygosity, and population differentiation were relatively consistent across all sampling periods. Overall, we found that “snapshot” or single-time sampling approaches may miss temporal variability in genetic composition that has important conservation implications, including early warning signs of decline in genetic diversity.