Experimental evidence for adaptive divergence in response to a warmed habitat reveals roles for morphology, allometry and parasite resistance.

Ectotherms are expected to be particularly vulnerable to climate change-driven increases in temperature. Understanding how populations adapt to novel thermal environments will be key for informing mitigation plans. We took advantage of threespine stickleback (Gasterosteus aculeatus) populations inhabiting adjacent geothermal (warm) and ambient (cold) habitats to test for adaptive evolutionary divergence using a field reciprocal transplant experiment. We found evidence for adaptive morphological divergence, as growth (length change) in non-native habitats related to head, posterior and total body shape. Higher growth in fish transplanted to a non-native habitat was associated with morphological shape closer to native fish. The consequences of transplantation were asymmetric with cold sourced fish transplanted to the warm habitat suffering from lower survival rates and greater parasite prevalence than warm sourced fish transplanted to the cold habitat. We also found divergent shape allometries that related to growth. Our findings suggest that wild populations can adapt quickly to thermal conditions, but immediate transitions to warmer conditions may be particularly difficult.

May-Thurner Syndrome: An Interesting Presentation of Recurrent, Unprovoked Deep Vein Thrombosis.

May-Thurner Syndrome (MTS) is a unique condition characterized by the compression of the left iliac vein by the right common iliac artery, which causes venous outflow obstruction and a high risk of venous sequelae. May-Thurner Syndrome is a condition that is primarily observed in females and is an uncommon cause of deep vein thrombosis (DVT). The more common presentation of DVT is in the lower left extremity, although there have been cases of right-sided formation. In this case report, we present a patient with unprovoked, recurrent, left-sided deep vein thrombosis in a 70-year-old woman. The aim of this case report is to highlight this uncommon condition and to suggest consideration of MTS in the setting of a patient with recurrent unprovoked DVTs of the same extremity.

Testing the predictability of morphological evolution in contrasting thermal environments.

Gaining the ability to predict population responses to climate change is a pressing concern. Using a "natural experiment," we show that testing for divergent evolution in wild populations from contrasting thermal environments provides a powerful approach, and likely an enhanced predictive power for responses to climate change. Specifically, we used a unique study system in Iceland, where freshwater populations of threespine sticklebacks (Gasterosteus aculeatus) are found in waters warmed by geothermal activity, adjacent to populations in ambient-temperature water. We focused on morphological traits across six pairs from warm and cold habitats. We found that fish from warm habitats tended to have a deeper mid-body, a subterminally orientated jaw, steeper craniofacial profile, and deeper caudal region relative to fish from cold habitats. Our common garden experiment showed that most of these differences were heritable. Population age did not appear to influence the magnitude or type of thermal divergence, but similar types of divergence between thermal habitats were more prevalent across allopatric than sympatric population pairs. These findings suggest that morphological divergence in response to thermal habitat, despite being relatively complex and multivariate, are predictable to a degree. Our data also suggest that the potential for migration of individuals between different thermal habitats may enhance nonparallel evolution and reduce our ability to predict responses to climate change.