Robson D.B.,The Manitoba Museum
Botany | Year: 2014
In Canada, silky prairie-clover (Dalea villosa var. villosa (Nutt.) Spreng) is a nationally rare plant, growing only in sand dunes in Saskatchewan and Manitoba. Previous research indicates that this species is incapable of self-pollination, making it dependent on insect pollinators for successful reproduction. The insect visitor community to D. villosa in Spruce Woods Provincial Park (SWPP), Manitoba, was documented and compared with that of 13 co-flowering plants that share some of its insect visitors. In total, 29 insect taxa were observed feeding on nectar or pollen from D. villosa. Hymenoptera were the most frequent visitors, comprising 60.7% of the taxa and making 93.5% of all visits. The visitation rate per stem to D. villosa (0.0042 stems·min-1) was the second highest of all of the plants with which it was compared. The insect visitor diversity was 4.0 (Simpson's reciprocal index), and the constancy index was 0.72. The high visitation rate, diversity, and constancy to this species may be due to a lack of competition for pollinators. Over half of the insect visitor taxa (54%) and visits (68%) were by omnivorous insects, as opposed to herbivorous ones. This means that there is interconnectivity between a mutualistic network involving D. villosa and several antagonistic networks.
Robson D.B.,The Manitoba Museum
Botany | Year: 2010
Flower-visiting insect activity to the rare Symphyotrichum sericeum (Vent.) G.L. Nesom and the common Solidago nemoralis Ait. var. longipetiolata (Mack. & Bush) Pal. & Steyerm. was examined to detect compositional and temporal similarities. A hand pollination experiment was conducted to determine whether pollen was limiting seed set. Of the 31 insect taxa that visited these plants, Bombus bifarius Cresson was the most common visitor to both species. More insect visitors of the Halictidae and Bombyliidae were received by S. sericeum than S. nemoralis, which received more visitors of the Syrphidae and Tachinidae. The insect visitation rate was not significantly different between the two plant species. Solidago nemoralis was visited by fewer insect taxa per day than S. sericeum, but the constancy of its visitors was higher. The insect visitor composition changed over time, with B. bifarius ignoring S. sericeum plants initially, then visiting them more frequently as the number of receptive S. nemoralis capitula declined. Hand pollination increased seed set in the ear- liest flowering capitula of S. sericeum, but not for those flowering during the peak. This research shows that the quantity of insect visits to the rare plant is comparable with that of the common plant but that pollination quality may be lower, particularly for early blooming capitula.
Young G.A.,The Manitoba Museum |
Young G.A.,University of Manitoba |
Hagadorn J.W.,Denver Museum of Nature and Science
Palaeoworld | Year: 2010
Fossils of cnidarian medusae are extremely rare, although reports of fossil " medusoids," most of which do not represent medusae, are rather common. Our previous inability to distinguish these fossils has hampered attempts to investigate patterns and processes within the medusozoan fossil record. Here we describe criteria for the recognition of bona fide fossil medusae and use them to assess the evolutionary, paleoenvironmental, and taphonomic history of the Medusozoa. Criteria include distinctive sedimentologic and taphonomic features that result from transport, stranding, and burial of hydrous clasts, as well as unequivocal body structures comparable to those of extant animals. Because the latter are uncommon, most fossil medusae remain in open nomenclature; many are assigned to stem-group scyphozoans.The majority of described medusae are associated with coastal depositional environments (such as tidal flats or lagoons). They rarely occur in oxygen-poor deeper-water facies. All medusan groups have long geologic histories. Scyphozoa are known from the Cambrian, but more derived scyphomedusae were not demonstrably present until the Carboniferous; Mesozoic scyphozoans are rather diverse. Hydromedusae are known from the Ordovician but may extend back to the Cambrian. The record of cubozoans is shorter and sparser; the oldest definite cubozoan is Carboniferous in age. © 2010 Elsevier Ltd and Nanjing Institute of Geology and Palaeontology, CAS.
Bizecki Robson D.,The Manitoba Museum
Botany | Year: 2013
Pollination facilitation can occur when plant species share pollinators. Whether facilitation occurs depends on the flowering period overlap (synchrony), number of shared insect visitors (similarity), quantity and quality of insect visits, and the subsequent impact on seed production. Western Silvery Aster (Symphyotrichum sericeum (Vent.) G.L. Nesom) is a rare, self-incompatible plant visited by a wide range of generalist insect species. There are 22 common plant species that may facilitate insect visitation to the rare plant by supporting shared pollinators. Plant species with low synchrony and high similarity with S. sericeum are potential facilitators. In contrast, plant species with high synchrony and similarity likely act as competitors as the aggregative response to increasing plant density was saturating, suggesting that synchronously flowering species do not increase insect visitations. Hymenoptera responded more strongly than Diptera to increases in flowering stem density. These data suggest that facilitation of insect visitation between plant species via a numerical response that extends the flower season is possible but not likely via an aggregative response. Restoration of S. sericeum may therefore be more successful if potentially facilitating plants are grown with it; further testing of the impact of potential facilitators on seed production in S. sericeum is required.
Elias R.J.,University of Manitoba |
Young G.A.,The Manitoba Museum |
Lee D.-J.,Andong National University |
Bae B.-Y.,Seoul National Science Museum
Geological Society Memoir | Year: 2013
During the Late Ordovician, Cincinnatian, the epicontinental seas and continental margin of Laurentia provided habitats that were suitable for corals. Biogeographical differentiation occurred within this equatorially placed continent, when corals were introduced to areas that had fundamentally different environments. There were four biogeographical divisions, characterized by distinctive faunas that included some endemic taxa: the Red River-Stony Mountain Province, Richmond Province, Edgewood Province and the less well understood, informal 'Continental Margin' Area. In each division, the potential for diversification and the capacity for diversity were determined by factors such as the duration and size of the division, the amount of immigration, the extent of evolution and biogeographical differentiation, faunal responses to changes in sea-level and climate, and the complexity of the ecological structure. The development of multiple biogeographical divisions, each contributing to overall diversity, enhanced the 'Great Ordovician Biodiversification Event'. During the latest Ordovician mass extinction, there was a reduction of diversity and loss of biogeographical divisions within Laurentia. The divisions were terminated when their characteristic taxa disappeared, in response to major environmental changes associated with glaciation in Gondwana and subsequent global warming. © The Geological Society of London 2013.