Demography and threats to population growth of Cirsium pitcheri, a threatened dune plant, in Wisconsin.

Multi-year and multi-site demographic data for rare plants allow researchers to observe threats and project population growth rates and thus long-term persistence of the species, generating knowledge, which allows for effective conservation planning. Demographic studies across more than a decade are extremely rare but allow for the effects of threats to be observed and assessed within the context of interannual environmental variation. We collected demographic data on the Threatened plant Cirsium pitcheri in two sites from 2011-2022. These sites were chosen because one exhibited the presence of non-native seed predators while the other did not, and we hypothesized that we would see declines and potentially extinction of the population threatened by predation. Over the course of our study, we observed additional threats, such as human trampling and high lake levels, which led to significant erosion, sand burial, and storm damage to plants. We find high interannual variation in vital rates and population growth rates for both populations, which mask the overall effects of predation. We observed dramatic declines in plant survivorship and population growth rates in both sites in the years with high lake levels. We conclude that high lake levels, which are expected to become more frequent with climate change, pose a significant threat to all near-shore populations of C. pitcheri.

Global conservation prioritization for the Orchidaceae.

Quantitative assessments of endemism, evolutionary distinctiveness and extinction threat underpin global conservation prioritization for well-studied taxa, such as birds, mammals, and amphibians. However, such information is unavailable for most of the world's taxa. This is the case for the Orchidaceae, a hyperdiverse and cosmopolitan family with incomplete phylogenetic and threat information. To define conservation priorities, we present a framework based on phylogenetic and taxonomic measures of distinctiveness and rarity based on the number of regions and the area of occupancy. For 25,434 orchid species with distribution data (89.3% of the Orchidaceae), we identify the Neotropics as hotspots for richness, New Guinea as a hotspot for evolutionary distinctiveness, and several islands that contain many rare and distinct species. Orchids have a similar proportion of monotypic genera as other Angiosperms, however, more taxonomically distinct orchid species are found in a single region. We identify 278 species in need of immediate conservation actions and find that more than 70% of these do not currently have an IUCN conservation assessment and are not protected in ex-situ collections at Botanical Gardens. Our study highlights locations and orchid species in urgent need of conservation and demonstrates a framework that can be applied to other data-deficient taxa.

Seed size and capitulum position drive germination and dormancy responses to projected warming for the threatened dune endemic Cirsium pitcheri (Asteraceae).

Among coastal plant species at risk from rapid environmental changes is the North American Great Lakes dune endemic Cirsium pitcheri. Despite being listed as federally threatened, little is known about how C. pitcheri seed attributes influence germination and dormancy-break patterns in the context of climate change. Following a previous work where we found differences in the number and weight of C. pitcheri seeds among capitulum positions and study sites, here we examine the effects of seed attributes (capitulum position, seed weight, and site of origin) on the proportion and timing of C. pitcheri seed germination under temperature treatments that simulate projected warming in the Great Lakes (20/10, 25/10, and 30/10°C day/night). Our results demonstrate that C. pitcheri produces diverse cohorts of seeds with seed attributes that significantly influence the timing and probability of germination over a 3-year soil seed bank. Cirsium pitcheri seed germination proportions were highest at 20°C and decreased successively at 25 and 30°C. Seeds from terminal capitula also had higher germination proportions and took longer to germinate than those from secondary capitula. Lastly, the effect of seed weight on germination probability depended on site of origin and capitulum position, with all effects varying in size and significance over time. Ultimately, our results highlight the considerable differences in germination patterns exhibited by seeds from different capitulum positions and sites of origin and provide insight into the dormancy-break patterns that C. pitcheri might experience under predicted temperature rise in the Great Lakes region of North America.

Automated conservation assessment of the orchid family with deep learning.

International Union for Conservation of Nature (IUCN) Red List assessments are essential for prioritizing conservation needs but are resource intensive and therefore available only for a fraction of global species richness. Automated conservation assessments based on digitally available geographic occurrence records can be a rapid alternative, but it is unclear how reliable these assessments are. We conducted automated conservation assessments for 13,910 species (47.3% of the known species in the family) of the diverse and globally distributed orchid family (Orchidaceae), for which most species (13,049) were previously unassessed by IUCN. We used a novel method based on a deep neural network (IUC-NN). We identified 4,342 orchid species (31.2% of the evaluated species) as possibly threatened with extinction (equivalent to IUCN categories critically endangered [CR], endangered [EN], or vulnerable [VU]) and Madagascar, East Africa, Southeast Asia, and several oceanic islands as priority areas for orchid conservation. Orchidaceae provided a model with which to test the sensitivity of automated assessment methods to problems with data availability, data quality, and geographic sampling bias. The IUC-NN identified possibly threatened species with an accuracy of 84.3%, with significantly lower geographic evaluation bias relative to the IUCN Red List and was robust even when data availability was low and there were geographic errors in the input data. Overall, our results demonstrate that automated assessments have an important role to play in identifying species at the greatest risk of extinction.

Evaluación Automatizada de la Conservación de la Familia Orchidaceae mediante Aprendizaje Profundo Resumen Los análisis de la Lista Roja de la Unión Internacional para la Conservación de la Naturaleza (UICN) son esenciales para la priorización de las necesidades de conservación, pero requieren de muchos recursos y por lo tanto están disponibles sólo para una fracción de la riqueza mundial de especies. Las evaluaciones automatizadas de la conservación basadas en los registros disponibles de presencia geográfica pueden ser una alternativa rápida pero no está claro cuán confiables son estas evaluaciones. Realizamos evaluaciones automatizadas de la conservación para 13,910 especies (47.3% de las especies conocidas de la familia) de la diversa y mundialmente distribuida familia de las orquídeas (Orchidaceae), en la cual la mayoría de las especies (13,049) no tenían una valoración previa por parte de la UICN. Usamos un método novedoso basado en una red neural profunda (IUC-NN). Identificamos 4,342 especies de orquídeas (31.2% de las especies evaluadas) como posiblemente amenazadas por la extinción (equivalente a las categorías de la UICN en peligro crítico [CR], en peligro [EN] o vulnerable [VU]) y a Madagascar, África Occidental, el sudeste de Asia y varias islas oceánicas como áreas prioritarias para la conservación de orquídeas. La familia Orchidaceae proporcionó un modelo con el cual probar la sensibilidad de los métodos de evaluación automatizada ante problemas con la disponibilidad de datos, la calidad de los datos y los sesgos de muestreo geográfico. La IUC-NN identificó posibles especies amenazadas con una certeza de 84.3% con un sesgo de evaluación geográfica significativamente más bajo en relación con la Lista Roja de la UICN y mostró solidez incluso cuando la disponibilidad de datos fue baja y hubo errores geográficos en los datos de entrada. En general, nuestros resultados demostraron que las evaluaciones automatizadas tienen un papel importante que desempeñar en la identificación de especies con mayor riesgo de extinción.

Nonadditive effects among threats on rare plant species.

The current loss of biodiversity has put 50,000 plant species at an elevated risk of extinction worldwide. Conserving at-risk species is often complicated by covariance or nonadditivity among threats, which makes it difficult to determine optimal management strategies. We sought to demographically quantify covariance and nonadditive effects of more threats on more rare plant species than ever attempted in a single analysis. We used 1082 population reports from 186 populations across 3 U.S. states of 27 rare, herbaceous plant species collected over 15 years by citizen scientists. We used a linear mixed-effects model with 4 threats and their interactions as fixed predictors, species as a random predictor, and annual growth rates as the response. We found a significant 3-way interaction on annual growth rates; rare plant population sizes were reduced by 46% during the time immediately after disturbance when populations were also browsed by deer (Odocoileus virginianus) and had high levels of encroachment by woody species. This nonadditive effect should be considered a major threat to the persistence of rare plant species. Our results highlight the need for comprehensive, multithreat assessments to determine optimal conservation actions.

Efectos No Acumulativos entre las Amenazas para las Especies Raras de Plantas Resumen La actual pérdida de biodiversidad ha colocado a 50,000 especies de plantas en un riesgo elevado de extinción global. La conservación de las especies en riesgo frecuentemente se complica por la covarianza o la no acumulabilidad entre las amenazas, lo que dificulta la determinación de las estrategias óptimas de manejo. Buscamos cuantificar demográficamente la covarianza y los efectos no acumulativos de más amenazas sobre un mayor número de especies raras de plantas, lo más que se ha intentado en un solo análisis. Utilizamos 1,082 reportes poblacionales tomados de 186 poblaciones en tres estados de los Estados Unidos. Estas poblaciones fueron de 27 especies raras de plantas herbáceas recolectadas a lo largo de 15 años por ciudadanos científicos. Usamos un modelo lineal de efectos mixtos con cuatro amenazas y sus interacciones como pronosticadoras fijas, las especies como pronosticadoras aleatorias y las tasas anuales de crecimiento como las respuestas. Encontramos una interacción significativa de tres vías en las tasas anuales de crecimiento; el tamaño poblacional de las plantas raras se redujo en un 46% durante el tiempo transcurrido inmediatamente después de una perturbación, cuando a la vez las poblaciones también eran ramoneadas por venados (Odocoileus virginianus) y tenían niveles altos de invasión por parte de especies leñosas. Este efecto no acumulativo debería considerarse una amenaza mayor para la persistencia de las especies raras de plantas. Nuestros resultados resaltan la necesidad de tener evaluaciones completas que consideren amenazas múltiples para así determinar las acciones óptimas de conservación.

Local differentiation and plasticity in size and sex expression in jack-in-the-pulpit, Arisaema triphyllum (Araceae).

The size advantage hypothesis suggests that natural selection will favor size-dependent sex expression when one sex gains more than the other by being large. But members of a minority sex will also have a higher reproductive value, on average. Thus, an individual's reproductive success depends on the reproductive decisions made by neighboring individuals. As a result, the optimal relationship between size and sex may differ among populations. In Arisaema triphyllum, the probability for an individual to be female increases with size, regardless of the character measured. A reciprocal transplant experiment showed the relationship between size and sexual expression is environmentally plastic. Plants originating from our two study sites became female at a larger average size when grown at one site than when grown at the other. In addition to environmental influence on sex expression, the experiment demonstrated genetic differences in the relationship between size and sex. Plants collected from one site became female at a larger size than those from the other, regardless of where they were grown. Thus, while the environment in which an individual was grown had a substantial influence on its sex expression, populations only a few kilometers apart have genetically different relationships between size and sex.

Periodic carbon flushing to roots of Quercus rubra saplings affects soil respiration and rhizosphere microbial biomass.

Patterns of root/shoot carbon allocation within plants have been studied at length. The extent, however, to which patterns of carbon allocation from shoots to roots affect the timing and quantity of organic carbon release from roots to soil is not known. We employed a novel approach to study how natural short-term variation in the allocation of carbon to roots may affect rhizosphere soil biology. Taking advantage of the semi-determinate phenology of young northern red oak (Quercus rubra L.), we examined how pulsed delivery of carbon from shoots to roots affected dynamics of soil respiration as well as microbial biomass and net nitrogen mineralization in the rhizosphere. Young Q. rubra exhibit (1) clear switches in the amount of carbon allocated below-ground that are non-destructively detected simply by observing pulsed shoot growth above-ground, and (2) multiple switches in internal carbon allocation during a single growing season, ensuring our ability to detect short-term effects of plant carbon allocation on rhizosphere biology separate from longer-term seasonal effects. In both potted oaks and oaks rooted in soil, soil respiration varied inversely with shoot flush stage through several oak shoot flushes. In addition, upon destructive harvest of potted oaks, microbial biomass in the rhizosphere of saplings with actively flushing shoots was lower than microbial biomass in the rhizosphere of saplings with shoots that were not flushing. Given that plants have evolved with their roots in contact with soil microbes, known species-specific carbon allocation patterns within plants may provide insight into interactions among roots, symbionts, and free-living microbes in the dynamic soil arena.