Tesla Inc. has lost its highest-ranking sales executive in North America, Troy Jones, the Wall Street Journal reported, citing people familiar with the matter. Jones, vice president of sales, service and delivery for the region, left the electric-vehicle maker after a 15-year tenure that began in 2010. His exit extends a string of senior departures at Tesla as the company contends with weakening demand in its two largest markets and rising competition from lower-priced rivals. Over the past year Tesla has also seen the departures of manufacturing chief Omead Afshar, battery engineer Drew Baglino and global public-policy head Rohan Patel, among others. Investors reacted to the news by sending Tesla shares down more than 1% in midday trading on Tuesday. The turnover in the upper ranks adds to pressure on Chief Executive Officer Elon Musk as Tesla works to revive sales and shift resources toward robotics and autonomous-driving initiatives.