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Biotic specialization holds information about the assembly, evolution, and stability of biological communities. Partner availabilities can play an important role in enabling species interactions, where uneven partner availabilities can bias estimates of biotic specialization when using phylogenetic diversity indices. It is therefore important to account for partner availability when characterizing biotic specialization using phylogenies. We developed an index, phylogenetic structure of specialization (PSS), that avoids bias from uneven partner availabilities by uncoupling the null models for interaction frequency and phylogenetic distance. We incorporate the deviation between observed and random interaction frequencies as weights into the calculation of partner phylogenetic α-diversity. To calculate the PSS index, we then compare observed partner phylogenetic α-diversity to a null distribution generated by randomizing phylogenetic distances among the same number of partners. PSS quantifies the phylogenetic structure (i.e., clustered, overdispersed, or random) of the partners of a focal species. We show with simulations that the PSS index is not correlated with network properties, which allows comparisons across multiple systems. We also implemented PSS on empirical networks of host-parasite, avian seed-dispersal, lichenized fungi-cyanobacteria, and hummingbird pollination interactions. Across these systems, a large proportion of taxa interact with phylogenetically random partners according to PSS, sometimes to a larger extent than detected with an existing method that does not account for partner availability. We also found that many taxa interact with phylogenetically clustered partners, while taxa with overdispersed partners were rare. We argue that species with phylogenetically overdispersed partners have often been misinterpreted as generalists when they should be considered specialists. Our results highlight the important role of randomness in shaping interaction networks, even in highly intimate symbioses, and provide a much-needed quantitative framework to assess the role that evolutionary history and symbiotic specialization play in shaping patterns of biodiversity. PSS is available as an R package at https://github.com/cjpardodelahoz/pss.

Peltigera serusiauxii is proposed here as a new species from Papua New Guinea and Sabah, northern Borneo (Malaysia). The species belongs to the polydactyloid clade of section Polydactylon. Because of its large thalli with a glabrous upper surface, this species was previously identified as P. dolichorhiza, but it differs by its polydactylon-type lower surface and the high amount of dolichorrhizin. It appears to be a strict specialist in its association with Nostoc phylogroup IX throughout its known distribution. This is one of many undescribed species remaining to be formally described within the genus Peltigera, especially in Asia and Australasia.

SummaryBiotic specialization holds information about the assembly, evolution and stability of biological communities. Phylogenetic diversity metrics have been used to quantify biotic specialization, but their current implementations do not adequately account for the availability of the interacting partners. Also, the overdispersed pattern of phylogenetic specialization has been misinterpreted as an attribute of generalists. We developed an approach that resolves these issues by accounting for partner availability to quantify the phylogenetic structure of specialization (i.e., clustered, overdispersed, or random) in ecological networks. We showed that our approach avoids biases of previous methods. We also implemented it on empirical networks of host–parasite, avian seed-dispersal, lichenized fungi– cyanobacteria and coral–dinoflagellate interactions. We found a large proportion of taxa that interact with phylogenetically random partners, in some cases to a larger extent than detected with an existing method that does not account for partner availability. We also found many taxa that interact with phylogenetically clustered partners, while taxa with overdispersed partners were rare. Our results highlight the important role of randomness in shaping interaction networks, even in highly intimate symbioses, and provide a much-needed quantitative framework to assess the role that evolutionary history and symbiotic specialization play in shaping patterns of biodiversity.

Seventy-four lichen species, identified from both modern and historical vouchers, are reported for Lizard Lick, Wake County, North Carolina. Like many granite flat rock areas in the southeastern United States, the Lizard Lick flora is a unique combination of Piedmont and Coastal Plain species. The Lizard Lick lichen flora shares 24 species in common with two similar, nearby granite flat rock sites, Temple Flat Rock Preserve and Turnipseed Nature Preserve. Species characteristic of granite flat rock habitats were found, including Peltula cylindrica and Pyrenopsis portoricensis; the latter collection represents the second record of this species for North America.

Seaweeds (macroalgae) accumulate heavy metals from seawater and can therefore serve as biological monitors of marine pollution. In this paper, we present data on the tissue chemistry of seaweeds from the area of Callahan Mine, an intertidal copper and zinc mine in Brooksville, ME, USA, abandoned in the 1970s and now designated as a Superfund site. The mine is located on the Goose Pond estuary, which drains into the ocean via a tidal waterfall at Goose Falls. Seaweed tissue samples from this estuary had the same relative concentrations of metals as had been reported previously in water samples from this location, with Zn > Cu > Pb > Cd. Ascophyllum nodosum, the most common macroalgal species in the area, had comparatively high levels of all four metals in samples from Goose Pond itself, while samples from Goose Falls tended to have substantially lower metal concentrations statistically indistinguishable from samples collected in nearby unpolluted sites. At Goose Falls, where seaweed diversity was ...

Phylogenetic studies of the lichenized fungal family Graphidaceae necessitate various nomenclatural changes. Tribe Wirthiotremateae is more narrowly circumscribed on the basis of new molecular data and phenotypical differences towards allied clades. The new genus Austrotrema is described to accommodate the three species of the Thelotrema bicinctulum group, Asteristion is resurrected for the seven species of the Chapsa platycarpa group, and Nadvornikia is expanded to include two non-mazaediate species in addition to its two mazaediate species. Asteristion australianum is newly described for Australian material previously identified as T. albo-olivaceum. Eleven new combinations are made: Asteristion alboannuliforme (Bas.: Thelotrema alboannuliforme), As. albo-olivaceum (Bas.: T. albo-olivaceum), As. cupulare (Bas.: T. cupulare), As. leucophthalmum (Bas.: T. leucophthalmum), As. platycarpoides (Bas.: T. platycarpoides), As. platycarpum (Bas.: T. platycarpum), Austrotrema bicinctulum (Bas.: T. bicinc...

Limestone is a distinctive substrate that has significant effects on soils and plants. The present study characterizes the diversity of vascular plants, bryophytes, and lichens at the Simonton Corner Quarry Preserve, an abandoned limestone quarry in Rockport, Maine, USA, which was in operation in the late 1800s. We document vascular plant diversity and associated edaphic features (i.e., soil pH and elemental chemistry) using 30 5×5 meter plots spread throughout the site. For vascular plants, 114 species in 96 genera and 50 families were observed; few of these species are known to prefer calcareous environments, and 38% are nonnative. Conversely, the soil- and rock-dwelling cryptogam biota, which comprises 21 moss species in 13 families and eight lichen species in three families, contains many calciphilic species. The bryoflora conspicuously lacks liverworts, whereas the lichen biota is dominated by cyanolichens. This study will inform future conservation and reclamation work at this and other hum...

The consequences of initial variability in reproductive effort on later pollination and fruit development have frequently been investigated with flower removal experiments. Often, plants produce many fewer fruits than flowers, so flower removal might not be expected to alter subsequent growth or development patterns all that much. Yet, many studies have demonstrated such changes even for species with low average fruit set, which begs for an explanation. Many (at least seven, by our count) such explanations have been reported in the literature, but experimental support for most is limited. In summer 2014, we conducted a field experiment on a lowbush blueberry (Vaccinium angustifolium) farm in Maine. In this experiment, we coupled flower removal with three other treatments, each designed to assess the validity of one of three often-cited hypotheses invoked to explain why growth and development changes occur following flower removal: 1) “Short-term nutrient shortages;” 2) “spatiotemporal limitations;” and 3) “the compound interest effect.” The three respective treatments—foliar nitrogen fertilization, positionally biased flower removal, and defoliation—were designed to either intensify or weaken the apparent effects of flower removal if the corresponding hypothesis had merit. As in a 2013 preliminary experiment, flower removal elicited several statistically significant growth and development changes in blueberry, including increases in final leaf area, ripe fruit weight, fruit ripening rate, and relative fruit production. The additional treatments also elicited several significant plant responses, though not always with concomitant flower removal effects as well. For example, fertilization generally increased fruit cluster mass by harvest, but flower removal itself had no such effect on cluster mass. Most observed interactive effects between flower removal and the additional treatments either ran counter to expectations, were limited in scope, or couldn't be unambiguously interpreted. For at least a few observed changes, none of the additional treatments significantly altered the effects of flower removal. We conclude that current hypotheses for the mechanistic basis for changes induced by flower removal are inadequate, at least for blueberry, a species with frequently low fruit set even when managed commercially. However, strong intellectual and economic imperatives exist to encourage further investigation into this open question.Plants grown in horticulture or occurring as adventives outside their native range can provide insight into species’ fundamental niche requirements that might not be evident from the native range, or realized niche, alone. Such occurrences can also identify conditions that support individual survival, but do not currently sustain positive population growth (i.e., a species’ ‘tolerance niche’). Further, in the context of rapid climate change, horticultural and adventive occurrences beyond current range edges might circumvent natural dispersal limitations and facilitate species range shifts. To explore these concepts in the field, we investigated the history and structure of five newly discovered populations of naturalized Magnolia tripetala near horticultural sites in western Massachusetts, USA. This tree species is native to the southeastern US, but has been grown horticulturally in the Northeast since the 1800s. However, naturalized populations had not been well documented in the region previously, raising the possibility that the species’ escape has been triggered by recent climate change. With tree coring and life stage surveys, we asked whether the naturalized populations exhibited synchronous patterns of establishment and expansion, suggestive of climatic release and a shift from tolerance niche to fundamental niche conditions in the region. Across the five sites, we documented 660 individuals, with populations ranging in size from 46 to 396 individuals, including seedlings, saplings, and reproduct

The paper reviews published botanical and pedological literature concerning gabbro in the California Floristic Province. Gabbro is a mafic plutonic rock that is common in the Sierra Nevada, Klamath Mountains, and Peninsular Ranges of the California Floristic Province. Its mineralogical and chemical compositions span the range between those of peridotite, an ultramafic rock, and diorite, a rock more silicic than gabbro. A broad range of nutrient element compositions makes gabbro soils extremely diverse substrates that harbor numerous rare and endemic plant species, particularly at the Pine Hill intrusive complex in El Dorado County, California. Several directions for further work are also suggested. More research is required to discern the poorly understood factors affecting endemism and plant distributions on gabbro soils. Attention should be paid to floristic differences between olivine gabbro, which chemically borders serpentine, and gabbro lacking olivine or containing more hornblende than olivine. A species list is provided which highlights rare, serpentine-preferring, and gabbro-endemic taxa reported from gabbro soils in the California Floristic Province.

Geochemistry and mineralogy of rocks play important roles in the occurrence of individual lichen species and assembly of lichen communities. Whereas lichens of metal-enriched settings have been a focus of study for many decades, only a few such lichen inventories exist for North America. We reexamined the lichen biota of Pine Hill, a serpentine outcrop on Little Deer Isle, Maine and Callahan Mine, a copper- and zinc-enriched Superfund site in Brooksville, Maine by conducting additional field surveys and reexamining unidentified taxa from previous collections. To better characterize the substrates upon which the lichens were found, we conducted elemental analyses via x-ray fluorescence and inductively coupled plasma-mass spectrometry on rock samples collected at Pine Hill and recorded pH, electrical conductivity, and elemental concentrations via inductively coupled plasma mass spectrometry on soil samples from Callahan Mine. The re-investigation of lichens of the two metal-enriched sites resulted in the addition of 20 taxa to Pine Hill and 10 taxa to Callahan Mine. These include Dermatocarpon leptophyllodes, Placynthiella hyporhoda, Pyrenocarpon thelostomum, and Vezdaea acicularis, all recorded for the first time from New England. In addition, we report the first documented records since the late 19th to early 20th century for New England of Porocyphus coccodes, Sarcosagium campestre, and Steinia geophana, and the first such record for Maine for Coccocarpia palmicola. Stereocaulon condensatum and S. subcoralloides, both considered as rare in New England, were also collected from Callahan Mine.