Morphological Species Delimitation in The Western Pond Turtle (Actinemys): Can Machine Learning Methods Aid in Cryptic Species Identification?

As the discovery of cryptic species has increased in frequency, there has been an interest in whether geometric morphometric data can detect fine-scale patterns of variation that can be used to morphologically diagnose such species. We used a combination of geometric morphometric data and an ensemble of five supervised machine learning methods (MLMs) to investigate whether plastron shape can differentiate two putative cryptic turtle species, Actinemys marmorata and Actinemys pallida. Actinemys has been the focus of considerable research due to its biogeographic distribution and conservation status. Despite this work, reliable morphological diagnoses for its two species are still lacking. We validated our approach on two datasets, one consisting of eight morphologically disparate emydid species, the other consisting of two subspecies of Trachemys (T. scripta scripta, T. scripta elegans). The validation tests returned near-perfect classification rates, demonstrating that plastron shape is an effective means for distinguishing taxonomic groups of emydids via MLMs. In contrast, the same methods did not return high classification rates for a set of alternative phylogeographic and morphological binning schemes in Actinemys. All classification hypotheses performed poorly relative to the validation datasets and no single hypothesis was unequivocally supported for Actinemys. Two hypotheses had machine learning performance that was marginally better than our remaining hypotheses. In both cases, those hypotheses favored a two-species split between A. marmorata and A. pallida specimens, lending tentative morphological support to the hypothesis of two Actinemys species. However, the machine learning results also underscore that Actinemys as a whole has lower levels of plastral variation than other turtles within Emydidae, but the reason for this morphological conservatism is unclear.

Medical and surgical management of early Q wave myocardial infarction. II. Effects on mortality and global and regional left ventricular function at 10 or more years of follow-up.

To determine the long-term effect of surgical reperfusion on survival and left ventricular function of patients with anterior and inferior Q wave myocardial infarction, 387 patients were followed up for greater than or equal to 10 years after early Q wave infarction. In the anterior infarction group, 102 received conventional therapy and 101 underwent surgical reperfusion. The overall hospital mortality rate in the medically and surgically treated patients was different (16.7% [17 of 102] versus 6.9% [7 of 101], p less than 0.05). The cumulative 13 year actuarial mortality rate widened between the anterior medical and surgical groups (54% versus 31%, p = 0.0003) by the adjusted Cox proportional hazards model. The hospital mortality rate with early reperfusion (that is, less than or equal to 6 h of symptom onset) was 2% (1 of 51), whereas the mortality rate with late reperfusion was 12% (6 of 50). The 13 year actuarial cumulative mortality rate was significantly lower in both the early and late reperfusion groups (30% and 33%, respectively) than in the conventional therapy group (54%, p = 0.0006). The mortality rate in patients receiving surgery after surviving initial medical therapy was 50% (15 of 30). In the survivors of anterior Q wave myocardial infarction, improved global ejection fraction was seen in the patients undergoing early (54 +/- 13%) and late (50 +/- 10%) surgery relative to those receiving conventional therapy (43 +/- 11%, p less than 0.05). Only the early reperfusion group had better regional function of the anterior wall than that of the conventional therapy group. Thus, ventricular function correlated with improved long-term survival. In the patients with inferior Q wave myocardial infarction, the overall hospital mortality rate in the medical and surgical groups was not different (6.1% [6 of 98] versus 4.6% [6 of 86], p = NS). Likewise, the 13 year actuarial cumulative mortality rate was not different between the medical and surgical groups overall (32% versus 30%, p = 0.29) by the adjusted Cox proportional hazards model. The hospital mortality rate in the early reperfusion group was lower than that in the late reperfusion group (2.0% [1 of 49] versus 8.1% [3 of 37], p = NS). The 13 year actuarial cumulative mortality rate was lower in the early surgical group compared with that in the medical group (19% versus 32%, p = 0.04). The late surgical group had a similar 13 year actuarial cumulative mortality rate to that of the medical group (47% versus 32%, respectively, p = 0.47).(ABSTRACT TRUNCATED AT 400 WORDS)

Ventricular fibrillation causes sudden death in Southeast Asian immigrants.

Young, male, Southeast Asian immigrants living in the United States have a high incidence of unexplained, sudden, nocturnal death. We report the cases of three patients, two Laotians and one Filipino, who were resuscitated and subsequently studied extensively. Each patient was having ventricular fibrillation when first examined by paramedics outside the hospital, and episodes of fibrillation recurred in the early hospital course. Clinical evaluation found no significant coronary atherosclerosis or structural cardiac disease. One patient is asymptomatic after 2 years; the second patient died suddenly at 4 months; and the third is asymptomatic but had inducible ventricular tachycardia on electrophysiologic testing 6 months after resuscitation. The mechanism of sudden death in young Southeast Asian men appears to be ventricular fibrillation. The cause of the arrhythmia is unclear, although in our patients the arrhythmia was not an isolated event; underlying predispositions to further cardiac arrest persisted.